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/FailoverDuringDeployTests.cs

@@ -19,6 +19,7 @@ public sealed class FailoverDuringDeployTests
     private static CancellationToken Ct => TestContext.Current.CancellationToken;
 
     /// <summary>Verifies that stopping node B shrinks the cluster to one up member.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Stopping_node_b_shrinks_cluster_to_one_up_member()
     {
@@ -34,6 +35,7 @@ public sealed class FailoverDuringDeployTests
     }
 
     /// <summary>Verifies that a restarted node B rejoins the cluster on the same port.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Restarted_node_b_rejoins_cluster_on_same_port()
     {
@@ -51,6 +53,7 @@ public sealed class FailoverDuringDeployTests
     }
 
     /// <summary>Verifies that a deployment started with node B down seals with one-node state.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Deployment_started_with_node_b_down_seals_with_one_node_state()
     {