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.ControlPlane.Tests/ConfigComposerTests.cs

@@ -10,6 +10,7 @@ namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests;
 public sealed class ConfigComposerTests : ControlPlaneActorTestBase
 {
     /// <summary>Verifies that an empty database produces a stable, reproducible hash.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Empty_database_produces_stable_hash()
     {
@@ -26,6 +27,7 @@ public sealed class ConfigComposerTests : ControlPlaneActorTestBase
     }
 
     /// <summary>Verifies that insertion order does not affect the configuration hash.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Same_rows_in_different_insert_orders_produce_same_hash()
     {
@@ -54,6 +56,7 @@ public sealed class ConfigComposerTests : ControlPlaneActorTestBase
     }
 
     /// <summary>Verifies that different database configurations produce different hashes.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Different_data_produces_different_hash()
     {
@@ -76,6 +79,7 @@ public sealed class ConfigComposerTests : ControlPlaneActorTestBase
     }
 
     /// <summary>Verifies that the revision hash is a 64-character lowercase hexadecimal string.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Hash_is_64_lowercase_hex_chars()
     {