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/ClusterFormationTests.cs

@@ -12,6 +12,7 @@ namespace ZB.MOM.WW.OtOpcUa.Host.IntegrationTests;
 public sealed class ClusterFormationTests
 {
     /// <summary>Verifies that two nodes form a 2-member cluster.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Two_nodes_form_a_2_member_cluster()
     {
@@ -29,6 +30,7 @@ public sealed class ClusterFormationTests
     }
 
     /// <summary>Verifies that both nodes see each other as role members.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Both_nodes_see_each_other_as_role_members()
     {