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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/OpcUaClientHistoryTests.cs

@@ -34,6 +34,7 @@ public sealed class OpcUaClientHistoryTests
     }
 
     /// <summary>Verifies ReadRawAsync throws without initialization.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task ReadRawAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -45,6 +46,7 @@ public sealed class OpcUaClientHistoryTests
     }
 
     /// <summary>Verifies ReadRawAsync with malformed NodeId returns empty result.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task ReadRawAsync_with_malformed_NodeId_returns_empty_result_not_throw()
     {
@@ -58,6 +60,7 @@ public sealed class OpcUaClientHistoryTests
     }
 
     /// <summary>Verifies ReadProcessedAsync throws without initialization.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task ReadProcessedAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -70,6 +73,7 @@ public sealed class OpcUaClientHistoryTests
     }
 
     /// <summary>Verifies ReadAtTimeAsync throws without initialization.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task ReadAtTimeAsync_without_initialize_throws_InvalidOperationException()
     {
@@ -81,6 +85,7 @@ public sealed class OpcUaClientHistoryTests
     }
 
     /// <summary>Verifies ReadEventsAsync throws NotSupportedException as documented.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task ReadEventsAsync_throws_NotSupportedException_as_documented()
     {