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/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/LiteDbConfigCacheTests.cs

@@ -24,6 +24,7 @@ public sealed class LiteDbConfigCacheTests : IDisposable
     };
 
     /// <summary>Verifies that payload is preserved through a write-then-read cycle.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Roundtrip_preserves_payload()
     {
@@ -38,6 +39,7 @@ public sealed class LiteDbConfigCacheTests : IDisposable
     }
 
     /// <summary>Verifies that GetMostRecentAsync returns the latest generation when multiple exist.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task GetMostRecent_returns_latest_when_multiple_generations_present()
     {
@@ -50,6 +52,7 @@ public sealed class LiteDbConfigCacheTests : IDisposable
     }
 
     /// <summary>Verifies that GetMostRecentAsync returns null for an unknown cluster.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task GetMostRecent_returns_null_for_unknown_cluster()
     {
@@ -58,6 +61,7 @@ public sealed class LiteDbConfigCacheTests : IDisposable
     }
 
     /// <summary>Verifies that Prune keeps the latest N generations and drops older ones.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Prune_keeps_latest_N_and_drops_older()
     {
@@ -81,6 +85,7 @@ public sealed class LiteDbConfigCacheTests : IDisposable
     }
 
     /// <summary>Verifies that writing the same cluster/generation twice replaces rather than duplicates.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Put_same_cluster_generation_twice_replaces_not_duplicates()
     {
@@ -102,6 +107,7 @@ public sealed class LiteDbConfigCacheTests : IDisposable
     // callers could both observe `existing is null` and both Insert.
     // ------------------------------------------------------------------------------------
     /// <summary>Verifies that concurrent PutAsync calls for the same cluster and generation do not create duplicates.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task PutAsync_concurrent_for_same_cluster_and_generation_does_not_duplicate()
     {