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/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests/FakeUpstream.cs

@@ -38,15 +38,12 @@ public sealed class FakeUpstream : ITagUpstreamSource
         }
     }
 
-    /// <summary>Reads the current value of a tag, or returns a bad-status snapshot if not set.</summary>
-    /// <param name="path">The tag path to read.</param>
+    /// <inheritdoc />
     public DataValueSnapshot ReadTag(string path)
         => _values.TryGetValue(path, out var v) ? v
             : new DataValueSnapshot(null, 0x80340000u, null, DateTime.UtcNow);
 
-    /// <summary>Subscribes an observer to tag changes for the given path.</summary>
-    /// <param name="path">The tag path to subscribe to.</param>
-    /// <param name="observer">The observer callback to invoke on tag changes.</param>
+    /// <inheritdoc />
     public IDisposable SubscribeTag(string path, Action<string, DataValueSnapshot> observer)
     {
         var list = _subs.GetOrAdd(path, _ => []);