docs: complete XML doc coverage (returns, summaries, inheritdoc)

Resolve all 622 issues flagged by the enhanced CommentChecker: add missing
<returns> tags (incl. the standard phrasing on non-generic Task methods),
add missing <summary> tags, and replace misused/redundant <inheritdoc/> on
members that override or implement nothing with real documentation.
Documentation-only — no behavior change; solution builds clean.

src/ZB.MOM.WW.ScadaBridge.AuditLog/Site/RingBufferFallback.cs

@@ -96,6 +96,7 @@ public sealed class RingBufferFallback
     /// must call <see cref="Complete"/> first.
     /// </summary>
     /// <param name="cancellationToken">Cancellation token to abort the async enumeration.</param>
+    /// <returns>An async sequence of buffered <see cref="AuditEvent"/> values in FIFO order.</returns>
     public async IAsyncEnumerable<AuditEvent> DrainAsync(
         [EnumeratorCancellation] CancellationToken cancellationToken)
     {

src/ZB.MOM.WW.ScadaBridge.AuditLog/Site/SiteAuditBacklogReporter.cs

@@ -69,7 +69,9 @@ public sealed class SiteAuditBacklogReporter : IHostedService, IDisposable
         _refreshInterval = refreshInterval ?? DefaultRefreshInterval;
     }
 
-    /// <inheritdoc />
+    /// <summary>Starts the background polling loop, running an immediate first probe before entering the timed cycle.</summary>
+    /// <param name="ct">Cancellation token signalling host shutdown.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public Task StartAsync(CancellationToken ct)
     {
         // Linked CTS lets StopAsync's cancellation AND the host's shutdown
@@ -123,14 +125,16 @@ public sealed class SiteAuditBacklogReporter : IHostedService, IDisposable
         }
     }
 
-    /// <inheritdoc />
+    /// <summary>Signals the polling loop to stop and waits for it to complete.</summary>
+    /// <param name="ct">Cancellation token (not used; the internal CTS governs shutdown).</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public Task StopAsync(CancellationToken ct)
     {
         _cts?.Cancel();
         return _loop ?? Task.CompletedTask;
     }
 
-    /// <inheritdoc />
+    /// <summary>Releases the internal <see cref="CancellationTokenSource"/> used to stop the polling loop.</summary>
     public void Dispose()
     {
         _cts?.Dispose();

src/ZB.MOM.WW.ScadaBridge.AuditLog/Site/SqliteAuditWriter.cs

@@ -244,7 +244,13 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
         cmd.ExecuteNonQuery();
     }
 
-    /// <inheritdoc />
+    /// <summary>
+    /// Enqueues an audit event for asynchronous batched persistence to SQLite.
+    /// Back-pressure is applied when the write channel is full.
+    /// </summary>
+    /// <param name="evt">The audit event to persist.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>A task that completes when the event has been persisted.</returns>
     public Task WriteAsync(AuditEvent evt, CancellationToken ct = default)
     {
         ArgumentNullException.ThrowIfNull(evt);
@@ -469,7 +475,13 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
         return CachedTelemetryKinds.Contains(kind);
     }
 
-    /// <inheritdoc />
+    /// <summary>
+    /// Returns up to <paramref name="limit"/> non-cached pending audit events, oldest first.
+    /// Cached-lifecycle kinds are excluded; use <see cref="ReadPendingCachedTelemetryAsync"/> for those.
+    /// </summary>
+    /// <param name="limit">Maximum number of rows to return.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>A task that resolves to a read-only list of pending audit events.</returns>
     public Task<IReadOnlyList<AuditEvent>> ReadPendingAsync(int limit, CancellationToken ct = default)
     {
         if (limit <= 0)
@@ -512,7 +524,13 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
         }
     }
 
-    /// <inheritdoc />
+    /// <summary>
+    /// Returns up to <paramref name="limit"/> pending cached-lifecycle audit events, oldest first.
+    /// Only rows with cached-call kinds (CachedSubmit, ApiCallCached, DbWriteCached, CachedResolve) are included.
+    /// </summary>
+    /// <param name="limit">Maximum number of rows to return.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>A task that resolves to a read-only list of pending cached-telemetry audit events.</returns>
     public Task<IReadOnlyList<AuditEvent>> ReadPendingCachedTelemetryAsync(
         int limit, CancellationToken ct = default)
     {
@@ -560,6 +578,7 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
     /// </summary>
     /// <param name="limit">Maximum number of rows to return.</param>
     /// <param name="ct">Cancellation token.</param>
+    /// <returns>A task that resolves to a read-only list of forwarded audit events.</returns>
     public Task<IReadOnlyList<AuditEvent>> ReadForwardedAsync(int limit, CancellationToken ct = default)
     {
         if (limit <= 0)
@@ -645,7 +664,15 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
         }
     }
 
-    /// <inheritdoc />
+    /// <summary>
+    /// Returns up to <paramref name="batchSize"/> pending or forwarded audit events
+    /// with <see cref="AuditEvent.OccurredAtUtc"/> &gt;= <paramref name="sinceUtc"/>, oldest first.
+    /// Used by the M6 reconciliation-pull handler.
+    /// </summary>
+    /// <param name="sinceUtc">Lower bound timestamp (UTC) for event occurrence.</param>
+    /// <param name="batchSize">Maximum number of rows to return.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>A task that resolves to a read-only list of audit events since the given timestamp.</returns>
     public Task<IReadOnlyList<AuditEvent>> ReadPendingSinceAsync(
         DateTime sinceUtc, int batchSize, CancellationToken ct = default)
     {
@@ -867,6 +894,7 @@ public class SqliteAuditWriter : IAuditWriter, ISiteAuditQueue, IAsyncDisposable
     }
 
     /// <summary>Asynchronously disposes the audit writer and releases resources.</summary>
+    /// <returns>A <see cref="ValueTask"/> that completes when all resources have been released.</returns>
     public async ValueTask DisposeAsync()
     {
         Task? writerLoop;

src/ZB.MOM.WW.ScadaBridge.AuditLog/Site/Telemetry/ClusterClientSiteAuditClient.cs

@@ -44,6 +44,9 @@ public sealed class ClusterClientSiteAuditClient : ISiteStreamAuditClient
     private readonly IActorRef _siteCommunicationActor;
     private readonly TimeSpan _askTimeout;
 
+    /// <summary>
+    /// Initializes a new instance that forwards audit telemetry to central via the site's <c>SiteCommunicationActor</c>.
+    /// </summary>
     /// <param name="siteCommunicationActor">
     /// The site's <c>SiteCommunicationActor</c> — it forwards the ingest command
     /// over the registered central ClusterClient and routes the reply back to

src/ZB.MOM.WW.ScadaBridge.AuditLog/Site/Telemetry/ISiteStreamAuditClient.cs

@@ -22,6 +22,7 @@ public interface ISiteStreamAuditClient
     /// </summary>
     /// <param name="batch">The batch of audit events to forward.</param>
     /// <param name="ct">Cancellation token for the operation.</param>
+    /// <returns>A task that resolves to the ingest acknowledgement containing accepted event IDs.</returns>
     Task<IngestAck> IngestAuditEventsAsync(AuditEventBatch batch, CancellationToken ct);
 
     /// <summary>
@@ -42,5 +43,6 @@ public interface ISiteStreamAuditClient
     /// </remarks>
     /// <param name="batch">The batch of cached-call telemetry packets to forward.</param>
     /// <param name="ct">Cancellation token for the operation.</param>
+    /// <returns>A task that resolves to the ingest acknowledgement containing accepted event IDs.</returns>
     Task<IngestAck> IngestCachedTelemetryAsync(CachedTelemetryBatch batch, CancellationToken ct);
 }