docs: complete XML doc comments via fixdocs (2757 to 131 findings)

Add missing <returns>/<param>/<summary>/<typeparam> tags and clean up
misused inheritdoc across 481 files so the documented API surface is
complete. Documentation-only (zero code lines changed). The 131 remaining
findings are inheritdoc-style warnings deliberately left to preserve
hand-written implementation rationale (plan-decision notes, race-condition
explanations).

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/DriverStatusSnapshotStoreTests.cs

@@ -17,6 +17,7 @@ public sealed class DriverStatusSnapshotStoreTests
     private static DriverHealthChanged Snap(string instance, string state = "Healthy") =>
         new("MAIN", instance, state, null, null, 0, new DateTime(2026, 5, 29, 0, 0, 0, DateTimeKind.Utc));
 
+    /// <summary>Verifies that Upsert raises SnapshotChanged with the stored snapshot.</summary>
     [Fact]
     public void Upsert_raises_SnapshotChanged_with_the_stored_snapshot()
     {
@@ -31,6 +32,7 @@ public sealed class DriverStatusSnapshotStoreTests
         received[0].ShouldBeSameAs(snap);
     }
 
+    /// <summary>Verifies that Upsert then TryGet returns the latest snapshot.</summary>
     [Fact]
     public void Upsert_then_TryGet_returns_the_latest_snapshot()
     {
@@ -42,6 +44,7 @@ public sealed class DriverStatusSnapshotStoreTests
         latest.State.ShouldBe("Degraded");
     }
 
+    /// <summary>Verifies that an unsubscribed handler stops receiving events after removal.</summary>
     [Fact]
     public void Unsubscribed_handler_stops_receiving_after_removal()
     {