Resolve Server-031..032 (re-triaged) + Server-038..043

Server-031: re-triaged. The recommended gateway-side
"skip-while-command-in-flight" guard is already in place at
WorkerClient.HeartbeatLoopAsync via WorkerClientOptions.HeartbeatStuckCeiling
(default 75s = 5× HeartbeatGrace). Two regression tests pin the
behaviour. Recommendation #1 (decouple worker-side _writeLock) is a
Worker-module concern (Worker-017 / Worker-023) and out of scope here.

Server-032: re-triaged. Recommendation #2 (rich diagnostic) is already
in EnqueueWorkerEventAsync, with #3 (overflow grace) absorbed by the
TryWrite → WriteAsync-with-timeout fall-through. Test
EnqueueWorkerEvent_WhenChannelFullPastTimeout_FaultsWithRichDiagnostic
pins the diagnostic string. Recommendation #1 (prose contract in
gateway.md / docs) is deferred — outside this pass's edit scope.

Server-038 (Security): EventsHub.SubscribeSession's missing per-session
ACL is documented with a TODO(per-session-acl) and a <remarks> block
explaining the v1 acceptance (any dashboard role can subscribe to any
session — non-secret metadata, redacted value logging). The per-session
ACL design lands in a follow-up once a session-scoped role exists.

Server-039 (Error handling): HubTokenService.Validate now rejects a
deserialized payload where both Name and NameIdentifier are null/empty.
New test file HubTokenServiceTests.cs covers the regression and five
sanity cases. TDD confirmed.

Server-040 (Conventions): MapGroupsToRoles gains a precedence comment
explaining "full literal match first, leading-RDN fallback;
OrdinalIgnoreCase via DashboardOptions.GroupToRole". Documentation-only.

Server-041 (Design adherence): EventStreamService.ProduceEventsAsync
wraps the broadcaster.Publish call in try/catch (Exception). The
producer loop and gRPC stream are no longer at the mercy of the
broadcaster's never-throw discipline. New regression test
StreamEventsAsync_WhenDashboardBroadcasterThrows_StillYieldsEventsAndDoesNotFaultSession.

Server-042 (Performance): DashboardSnapshotPublisher.ExecuteAsync now
mirrors AlarmsHubPublisher's reconnect loop — wraps the await foreach
in a while-not-cancelled, catches general exceptions, and Task.Delays
5s before retrying. An internal ctor accepts a shorter delay for the
test. New test file DashboardSnapshotPublisherTests.cs covers the
throw-then-yield reconnect path and the normal-completion case.

Server-043 (Documentation): HubTokenService class XML doc gains a
<remarks> describing the singleton lifetime, the two consumer scopes
(DashboardHubConnectionFactory scoped, HubTokenAuthenticationHandler
transient), and the thread-safety contract.

Verification: dotnet build src/ZB.MOM.WW.MxGateway.slnx clean
(0 warnings / 0 errors); src/ZB.MOM.WW.MxGateway.Tests 486/486 passing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardAuthenticator.cs

@@ -154,6 +154,13 @@ public sealed class DashboardAuthenticator(
         foreach (string group in groups)
         {
             string normalizedGroup = group.Trim();
+
+            // Lookup precedence (Server-040): the full literal group string is
+            // tried first; only if that misses do we fall back to the leading
+            // RDN value (e.g. "GwAdmin" extracted from
+            // "ou=GwAdmin,ou=groups,..."). The map's comparer is
+            // OrdinalIgnoreCase (see DashboardOptions.GroupToRole), so e.g.
+            // "GwAdmin" and "gwadmin" both match.
             if (groupToRole.TryGetValue(normalizedGroup, out string? mapped)
                 || groupToRole.TryGetValue(ExtractFirstRdnValue(normalizedGroup), out mapped))
             {