docs: backfill XML documentation across 756 files

Adds <summary>, <param>, <typeparam>, and <inheritdoc/> tags to public
members surfaced by commentchecker — resolves 5,847 of 5,869 issues
(99.6%) across three /fixdocs passes.

tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/FleetStatusBroadcasterTests.cs

@@ -10,6 +10,7 @@ namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests;
 
 public sealed class FleetStatusBroadcasterTests : ControlPlaneActorTestBase
 {
+    /// <summary>Verifies that the self member's join appears in the initial fleet status snapshot.</summary>
     [Fact]
     public void Self_member_up_lands_in_snapshot()
     {
@@ -22,6 +23,7 @@ public sealed class FleetStatusBroadcasterTests : ControlPlaneActorTestBase
         snapshot.Nodes.Any(n => n.Health == FleetNodeHealth.Healthy).ShouldBeTrue();
     }
 
+    /// <summary>Verifies that heartbeat messages update the node revision in the next broadcast.</summary>
     [Fact]
     public void Heartbeat_updates_revision_in_next_snapshot()
     {