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.Host.IntegrationTests/DeployHappyPathTests.cs

@@ -19,6 +19,7 @@ public sealed class DeployHappyPathTests
     private static CancellationToken Ct => TestContext.Current.CancellationToken;
 
     /// <summary>Verifies that StartDeployment seals after both nodes apply.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task StartDeployment_seals_after_both_nodes_apply()
     {
@@ -55,6 +56,7 @@ public sealed class DeployHappyPathTests
     }
 
     /// <summary>Verifies that replaying dispatch to same revision is idempotent and a no-op.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Replaying_dispatch_to_same_revision_is_idempotent_no_op()
     {