docs(tests): fix CommentChecker findings across tests/ — 13,392 → 0 (repo-wide scan clean)

Comment/XML-doc changes only:
- add summaries to ~10k test methods, fixtures, fakes and helpers
  (+ <param> on theories, <returns> on async Task methods,
  <inheritdoc/> on interface implementations the checker can resolve)
- strip ~2.6k project-tracking references (WP*, P*-*, row-NN, Task N,
  #NN, Component-0NN) from comments, keeping the explanatory text;
  reword false positives in comments only
- real docs on fakes implementing BCL/library interfaces
  (IDisposable, ILogger, IOptionsMonitor, IAsyncLifetime)
- reword the last 5 src/ false positives (CWE-1236, failures-1,
  year-0001, M365)

Only non-comment edits: four one-line nested classes split across lines
so members can carry docs. Build 0 errors / 0 warnings.

tests/ZB.MOM.WW.ScadaBridge.NotificationOutbox.Tests/NotificationOutboxActorPurgeTests.cs

@@ -13,7 +13,7 @@ using ZB.MOM.WW.ScadaBridge.NotificationOutbox.Tests.TestSupport;
 namespace ZB.MOM.WW.ScadaBridge.NotificationOutbox.Tests;
 
 /// <summary>
-/// Task 16: Tests for the <see cref="NotificationOutboxActor"/> daily purge job — the
+/// Tests for the <see cref="NotificationOutboxActor"/> daily purge job — the
 /// periodic sweep that bulk-deletes terminal notification rows older than
 /// <see cref="NotificationOutboxOptions.TerminalRetention"/> via
 /// <see cref="INotificationOutboxRepository.DeleteTerminalOlderThanAsync"/>.
@@ -51,6 +51,7 @@ public class NotificationOutboxActorPurgeTests : TestKit
             NullLogger<NotificationOutboxActor>.Instance)));
     }
 
+    /// <summary>Verifies that a purge tick deletes terminal rows using a cutoff of the current UTC time minus the terminal retention.</summary>
     [Fact]
     public void PurgeTick_DeletesTerminalRows_WithCutoffAtUtcNowMinusTerminalRetention()
     {
@@ -76,6 +77,7 @@ public class NotificationOutboxActorPurgeTests : TestKit
                 Arg.Any<CancellationToken>()));
     }
 
+    /// <summary>Verifies that a faulted purge does not crash the actor and a later purge still runs.</summary>
     [Fact]
     public void FaultedPurge_DoesNotCrashActor_AndSubsequentPurgeStillRuns()
     {