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/Browsing/BrowseSessionRegistryTests.cs

@@ -9,6 +9,7 @@ namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Browsing;
 /// concurrent-registration behaviour.</summary>
 public sealed class BrowseSessionRegistryTests
 {
+    /// <summary>Verifies that a registered session can be retrieved by its token.</summary>
     [Fact]
     public void Register_then_TryGet_returns_session()
     {
@@ -22,6 +23,7 @@ public sealed class BrowseSessionRegistryTests
         got.ShouldBeSameAs((IBrowseSession)session);
     }
 
+    /// <summary>Verifies that looking up an unknown token returns false.</summary>
     [Fact]
     public void TryGet_unknown_returns_false()
     {
@@ -31,6 +33,7 @@ public sealed class BrowseSessionRegistryTests
         got.ShouldBeNull();
     }
 
+    /// <summary>Verifies that a removed session can no longer be retrieved.</summary>
     [Fact]
     public void TryRemove_then_TryGet_returns_false()
     {
@@ -43,6 +46,8 @@ public sealed class BrowseSessionRegistryTests
         registry.TryGet(session.Token, out _).ShouldBeFalse();
     }
 
+    /// <summary>Verifies that concurrent registrations from many tasks are all visible in the snapshot.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Concurrent_Register_from_many_tasks_all_visible_in_Snapshot()
     {