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/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/HistoryViewModelTests.cs

@@ -60,6 +60,7 @@ public class HistoryViewModelTests
     }
 
     /// <summary>Verifies that a raw history read populates results correctly.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ReadHistoryCommand_Raw_PopulatesResults()
     {
@@ -77,6 +78,7 @@ public class HistoryViewModelTests
     }
 
     /// <summary>Verifies that an aggregate history read populates results correctly.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ReadHistoryCommand_Aggregate_PopulatesResults()
     {
@@ -94,6 +96,7 @@ public class HistoryViewModelTests
     }
 
     /// <summary>Verifies that the read history command clears previous results before loading new ones.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ReadHistoryCommand_ClearsResultsBefore()
     {
@@ -107,6 +110,7 @@ public class HistoryViewModelTests
     }
 
     /// <summary>Verifies that the loading state is false after the read history command completes.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ReadHistoryCommand_IsLoading_FalseAfterComplete()
     {
@@ -158,6 +162,7 @@ public class HistoryViewModelTests
     }
 
     /// <summary>Verifies that read history command errors are displayed in the results.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ReadHistoryCommand_Error_ShowsErrorInResults()
     {