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.FOCAS.Tests/FocasScaffoldingTests.cs

@@ -201,6 +201,7 @@ public sealed class FocasScaffoldingTests
     }
 
     /// <summary>Verifies InitializeAsync parses device addresses correctly.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task InitializeAsync_parses_device_addresses()
     {
@@ -221,6 +222,7 @@ public sealed class FocasScaffoldingTests
     }
 
     /// <summary>Verifies InitializeAsync faults on malformed addresses.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task InitializeAsync_malformed_address_faults()
     {
@@ -235,6 +237,7 @@ public sealed class FocasScaffoldingTests
     }
 
     /// <summary>Verifies ShutdownAsync clears all devices.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ShutdownAsync_clears_devices()
     {