refactor(sessions): remove the dead ISessionManager.ReadEventsAsync chain

ISessionManager.ReadEventsAsync had zero production call sites: the worker
event channel is drained once by GatewaySession.MapWorkerEventsAsync (the
distributor pump), and every consumer — gRPC subscribers, the dashboard
mirror, the alarm monitor — attaches to the distributor. The interface
member, SessionManager's forwarder, and GatewaySession.ReadEventsAsync are
gone; IWorkerClient/WorkerClient.ReadEventsAsync is untouched, it is the
live worker-channel claim.

No test was removed or rewired: nothing invoked the member through the
interface. Nine ISessionManager test fakes carried a required-member stub
(seven threw NotSupportedException or yielded nothing; EventStreamServiceTests
and GatewaySessionDashboardMirrorTests forwarded to the session; the two
MxAccessGatewayService fakes yielded their Events list) — all nine stubs were
deleted. The MxAccessGatewayService suites' streaming tests already run
through FakeEventStreamService, which reads the same Events list, so their
coverage is unchanged; only the now-inaccurate doc comments on Events /
LastReadEventsSessionId were reworded.

The MapWorkerEventsAsync comment no longer describes a twin to keep in step;
it now states the single-reader claim directly. docs/Sessions.md drops
ReadEventsAsync from the SessionManager member list and from the Run-state
prose. The 2026-08-15 deferred-remediation as-built note records the removal.

docs/Sessions.md

@@ -49,7 +49,7 @@ public void TransitionTo(SessionState nextState)
 
 ### SessionManager (ISessionManager)
 
-`SessionManager` is the orchestrator. It exposes `OpenSessionAsync`, `TryGetSession`, `InvokeAsync`, `ReadEventsAsync`, `CloseSessionAsync`, `KillWorkerAsync`, `CloseExpiredLeasesAsync`, and `ShutdownAsync`. It composes `ISessionRegistry`, `ISessionWorkerClientFactory`, `GatewayMetrics`, and `GatewayOptions`.
+`SessionManager` is the orchestrator. It exposes `OpenSessionAsync`, `TryGetSession`, `InvokeAsync`, `CloseSessionAsync`, `KillWorkerAsync`, `CloseExpiredLeasesAsync`, and `ShutdownAsync`. It composes `ISessionRegistry`, `ISessionWorkerClientFactory`, `GatewayMetrics`, and `GatewayOptions`.
 
 `CloseSessionAsync` and `KillWorkerAsync` are both end-of-life paths but differ in what they offer the worker:
 
@@ -191,7 +191,7 @@ The order — fault, deregister, dispose, release slot, record metric, log, reth
 
 ### Run
 
-While `Ready`, callers reach the worker through `SessionManager.InvokeAsync` or `ReadEventsAsync`. Both delegate to `GatewaySession`, which checks the state under lock and updates `LastClientActivityAt` on every invocation. `GatewaySession` also exposes typed bulk helpers (`AddItemBulkAsync`, `SubscribeBulkAsync`, etc.) that wrap `WorkerCommand` round-trips and translate non-`Ok` `ProtocolStatus` replies into `SessionManagerException` with `SessionNotReady`.
+While `Ready`, callers reach the worker through `SessionManager.InvokeAsync`, which delegates to `GatewaySession`, which checks the state under lock and updates `LastClientActivityAt` on every invocation. Events do not travel this path: every consumer attaches to the session's `SessionEventDistributor` instead (see below), so the manager exposes no event-read member. `GatewaySession` also exposes typed bulk helpers (`AddItemBulkAsync`, `SubscribeBulkAsync`, etc.) that wrap `WorkerCommand` round-trips and translate non-`Ok` `ProtocolStatus` replies into `SessionManagerException` with `SessionNotReady`.
 
 Event streaming uses `AttachEventSubscriber` which returns a disposable lease. When `allowMultipleSubscribers` is false (single-subscriber mode) a second attach throws `EventSubscriberAlreadyActive`; this prevents two gRPC streams from racing on the same worker event channel. When it is true, up to `MaxEventSubscribersPerSession` concurrent external subscribers are allowed and the next attach throws `EventSubscriberLimitReached`. The count-check-and-increment is atomic under the session lock, so concurrent attaches can never exceed the cap. The gateway-owned internal dashboard mirror subscriber is registered directly on the distributor and does not count toward the cap. Active event subscribers keep the session lease from expiring until the stream is disposed.
 

docs/plans/2026-08-15-deferred-remediation.md

@@ -321,7 +321,8 @@ is worth keeping, this is the record.
 through `ISessionManager.ReadEventsAsync`. That interface member itself has zero
 production call sites — only test fakes implement and exercise it. Deleting it is a
 mechanical but wide change (~15 test-fake touches), so it is recorded as a follow-up
-rather than done here.
+rather than done here. Removed by `docs/plans/2026-08-17-deferred-closeout.md` Task 1,
+2026-08-17.
 
 **Task 5 — dashboard event feed, two review rounds.** Review caught two races that
 the first cut did not have. First, subscription lifetime: subscriptions are now

src/ZB.MOM.WW.MxGateway.Server/Sessions/GatewaySession.cs

@@ -765,13 +765,11 @@ public sealed class GatewaySession
     // distributor guarantees a single consumer) and maps each frame to the public MxEvent,
     // preserving worker order. Mirrors the former ProduceEventsAsync mapping exactly.
     //
-    // This deliberately duplicates the three lines of ReadEventsAsync rather than enumerating
-    // it: every worker event crosses this source, and routing it through a second pure
-    // pass-through iterator cost two extra MoveNextAsync state-machine hops per event for no
-    // semantic value. ReadEventsAsync stays for ISessionManager.ReadEventsAsync; keep the two
-    // bodies in step. Only one of them may run per attach — WorkerClient.ReadEventsAsync
-    // single-reader-claims the event channel and throws on a second consumer — and on the
-    // distributor path that one consumer is this method.
+    // This is the session's only reader of the worker event channel: every gateway consumer —
+    // gRPC subscribers, the dashboard mirror, the alarm monitor — attaches to the distributor
+    // this source feeds. WorkerClient.ReadEventsAsync single-reader-claims that channel and
+    // throws on a second consumer, so any future path that drains it directly fails loudly
+    // rather than splitting events.
     private async IAsyncEnumerable<MxEvent> MapWorkerEventsAsync(
         [EnumeratorCancellation] CancellationToken cancellationToken)
     {
@@ -1522,33 +1520,6 @@ public sealed class GatewaySession
             cancellationToken);
     }
 
-    /// <summary>
-    /// Reads events from the worker as an asynchronous enumerable stream.
-    /// </summary>
-    /// <param name="cancellationToken">Token to cancel the asynchronous operation.</param>
-    /// <remarks>
-    ///     Backs <c>ISessionManager.ReadEventsAsync</c>. The distributor does <em>not</em> come
-    ///     through here — <c>MapWorkerEventsAsync</c> inlines this body to save a per-event
-    ///     iterator hop, so changes made here belong there too. The two are mutually exclusive
-    ///     per attach: <see cref="IWorkerClient.ReadEventsAsync"/> claims the worker event
-    ///     channel for a single reader and throws on the second consumer.
-    /// </remarks>
-    /// <returns>An asynchronous stream of worker events.</returns>
-    public async IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-        [EnumeratorCancellation] CancellationToken cancellationToken)
-    {
-        IWorkerClient workerClient = await GetReadyWorkerClientAsync(cancellationToken).ConfigureAwait(false);
-        TouchClientActivity(_eventStreaming.TimeProvider.GetUtcNow());
-
-        await foreach (WorkerEvent workerEvent in workerClient
-            .ReadEventsAsync(cancellationToken)
-            .WithCancellation(cancellationToken)
-            .ConfigureAwait(false))
-        {
-            yield return workerEvent;
-        }
-    }
-
     /// <summary>
     /// Closes the session and shuts down the worker process.
     /// </summary>

src/ZB.MOM.WW.MxGateway.Server/Sessions/ISessionManager.cs

@@ -35,14 +35,6 @@ public interface ISessionManager
         WorkerCommand command,
         CancellationToken cancellationToken);
 
-    /// <summary>Reads events streamed from the worker for the specified session.</summary>
-    /// <param name="sessionId">Identifier of the session.</param>
-    /// <param name="cancellationToken">Token to cancel the asynchronous operation.</param>
-    /// <returns>Events emitted by the worker.</returns>
-    IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-        string sessionId,
-        CancellationToken cancellationToken);
-
     /// <summary>Closes a session and terminates its worker process.</summary>
     /// <param name="sessionId">Identifier of the session to close.</param>
     /// <param name="cancellationToken">Token to cancel the asynchronous operation.</param>

src/ZB.MOM.WW.MxGateway.Server/Sessions/SessionManager.cs

@@ -187,16 +187,6 @@ public sealed class SessionManager : ISessionManager
         }
     }
 
-    /// <inheritdoc />
-    public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-        string sessionId,
-        CancellationToken cancellationToken)
-    {
-        GatewaySession session = GetRequiredSession(sessionId);
-
-        return session.ReadEventsAsync(cancellationToken);
-    }
-
     /// <inheritdoc />
     public async Task<SessionCloseResult> CloseSessionAsync(
         string sessionId,

src/ZB.MOM.WW.MxGateway.Tests/Alarms/AlarmFailoverEndToEndTests.cs

@@ -464,11 +464,6 @@ public sealed class AlarmFailoverEndToEndTests
             return Task.FromResult(new WorkerCommandReply { Reply = reply });
         }
 
-        /// <inheritdoc />
-        public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            CancellationToken cancellationToken) => throw new NotSupportedException();
-
         /// <inheritdoc />
         public bool TryGetSession(string sessionId, [MaybeNullWhen(false)] out GatewaySession session)
         {

src/ZB.MOM.WW.MxGateway.Tests/Alarms/GatewayAlarmMonitorAttachOrderTests.cs

@@ -618,11 +618,6 @@ public sealed class GatewayAlarmMonitorAttachOrderTests
             return new WorkerCommandReply { Reply = reply };
         }
 
-        /// <inheritdoc />
-        public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            CancellationToken cancellationToken) => throw new NotSupportedException();
-
         /// <inheritdoc />
         public bool TryGetSession(string sessionId, [MaybeNullWhen(false)] out GatewaySession session)
         {

src/ZB.MOM.WW.MxGateway.Tests/Alarms/GatewayAlarmMonitorProviderModeTests.cs

@@ -777,11 +777,6 @@ public sealed class GatewayAlarmMonitorProviderModeTests
             return Task.FromResult(new WorkerCommandReply { Reply = reply });
         }
 
-        /// <inheritdoc />
-        public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            CancellationToken cancellationToken) => throw new NotSupportedException();
-
         /// <inheritdoc />
         public bool TryGetSession(string sessionId, [MaybeNullWhen(false)] out GatewaySession session)
         {

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardLiveDataServiceTests.cs

@@ -261,10 +261,6 @@ public sealed class DashboardLiveDataServiceTests
             CancellationToken cancellationToken) =>
             throw new NotSupportedException();
 
-        /// <inheritdoc />
-        public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(string sessionId, CancellationToken cancellationToken) =>
-            throw new NotSupportedException();
-
         /// <inheritdoc />
         public Task<SessionCloseResult> KillWorkerAsync(
             string sessionId,

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardSessionAdminServiceTests.cs

@@ -370,14 +370,6 @@ public sealed class DashboardSessionAdminServiceTests
             throw new NotSupportedException();
         }
 
-        /// <inheritdoc />
-        public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            CancellationToken cancellationToken)
-        {
-            throw new NotSupportedException();
-        }
-
         /// <inheritdoc />
         public Task<SessionCloseResult> CloseSessionAsync(
             string sessionId,

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/EventStreamServiceTests.cs

@@ -761,14 +761,6 @@ public sealed class EventStreamServiceTests
             return Task.FromResult(new WorkerCommandReply());
         }
 
-        /// <inheritdoc />
-        public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            CancellationToken cancellationToken)
-        {
-            return _sessions[sessionId].ReadEventsAsync(cancellationToken);
-        }
-
         /// <inheritdoc />
         public Task<SessionCloseResult> CloseSessionAsync(
             string sessionId,

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/MxAccessGatewayServiceConstraintTests.cs

@@ -935,19 +935,6 @@ public sealed class MxAccessGatewayServiceConstraintTests
             return Task.FromResult(InvokeReply);
         }
 
-        /// <inheritdoc />
-        public async IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
-        {
-            foreach (WorkerEvent ev in Events)
-            {
-                cancellationToken.ThrowIfCancellationRequested();
-                await Task.Yield();
-                yield return ev;
-            }
-        }
-
         /// <inheritdoc />
         public Task<SessionCloseResult> CloseSessionAsync(
             string sessionId,

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Grpc/MxAccessGatewayServiceTests.cs

@@ -517,7 +517,7 @@ public sealed class MxAccessGatewayServiceTests
         /// <summary>The last owner key id passed to OpenSessionAsync.</summary>
         public string? LastOwnerKeyId { get; private set; }
 
-        /// <summary>The last session ID passed to ReadEventsAsync.</summary>
+        /// <summary>The last session ID the event stream service was asked to stream.</summary>
         public string? LastReadEventsSessionId { get; private set; }
 
         /// <summary>The last worker command passed to InvokeAsync.</summary>
@@ -540,10 +540,10 @@ public sealed class MxAccessGatewayServiceTests
         /// <summary>The number of times InvokeAsync was called.</summary>
         public int InvokeCount { get; private set; }
 
-        /// <summary>The events to return from ReadEventsAsync.</summary>
+        /// <summary>The events the fake event stream service replays for this manager.</summary>
         public List<WorkerEvent> Events { get; } = [];
 
-        /// <summary>Records the session ID passed to ReadEventsAsync.</summary>
+        /// <summary>Records the session ID the event stream service was asked to stream.</summary>
         /// <param name="sessionId">Identifier of the session.</param>
         public void RecordReadEventsSessionId(string sessionId)
         {
@@ -602,20 +602,6 @@ public sealed class MxAccessGatewayServiceTests
             return Task.FromResult(InvokeReply);
         }
 
-        /// <inheritdoc />
-        public async IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            [EnumeratorCancellation] CancellationToken cancellationToken)
-        {
-            LastReadEventsSessionId = sessionId;
-            foreach (WorkerEvent workerEvent in Events)
-            {
-                cancellationToken.ThrowIfCancellationRequested();
-                await Task.Yield();
-                yield return workerEvent;
-            }
-        }
-
         /// <inheritdoc />
         public Task<SessionCloseResult> CloseSessionAsync(
             string sessionId,

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Sessions/GatewaySessionDashboardMirrorTests.cs

@@ -347,11 +347,6 @@ public sealed class GatewaySessionDashboardMirrorTests
             WorkerCommand command,
             CancellationToken cancellationToken) => Task.FromResult(new WorkerCommandReply());
 
-        /// <inheritdoc />
-        public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            CancellationToken cancellationToken) => session.ReadEventsAsync(cancellationToken);
-
         /// <inheritdoc />
         public Task<SessionCloseResult> CloseSessionAsync(
             string sessionId,

src/ZB.MOM.WW.MxGateway.Tests/Security/Authorization/GatewayGrpcAuthorizationInterceptorTests.cs

@@ -848,14 +848,6 @@ public sealed class GatewayGrpcAuthorizationInterceptorTests
             return Task.FromResult(new WorkerCommandReply());
         }
 
-        /// <inheritdoc />
-        public IAsyncEnumerable<WorkerEvent> ReadEventsAsync(
-            string sessionId,
-            CancellationToken cancellationToken)
-        {
-            return AsyncEnumerable.Empty<WorkerEvent>();
-        }
-
         /// <inheritdoc />
         public Task<SessionCloseResult> CloseSessionAsync(
             string sessionId,