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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests/AbLegacyDisposeAndResolveHostTests.cs

@@ -18,6 +18,7 @@ public sealed class AbLegacyDisposeAndResolveHostTests
     // ---- Driver.AbLegacy-011 ----
 
     /// <summary>Verifies that Dispose performs teardown without blocking on async operations.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Dispose_runs_teardown_without_blocking_on_async_wait()
     {
@@ -47,6 +48,7 @@ public sealed class AbLegacyDisposeAndResolveHostTests
     }
 
     /// <summary>Verifies that Dispose can be called multiple times without throwing.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Dispose_is_idempotent()
     {
@@ -61,6 +63,7 @@ public sealed class AbLegacyDisposeAndResolveHostTests
     }
 
     /// <summary>Verifies that Dispose does not deadlock under a single-threaded synchronization context.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Dispose_under_single_threaded_sync_context_does_not_deadlock()
     {