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/FocasHandleRecycleTests.cs

@@ -7,6 +7,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests;
 public sealed class FocasHandleRecycleTests
 {
     /// <summary>Verifies that the recycle loop disposes clients on interval and reopens fresh ones.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Recycle_loop_disposes_client_on_interval_reads_reopen_fresh_one()
     {
@@ -40,6 +41,7 @@ public sealed class FocasHandleRecycleTests
     }
 
     /// <summary>Verifies that the recycle loop stays off when not enabled.</summary>
+    /// <returns>A task that represents the asynchronous test operation.</returns>
     [Fact]
     public async Task Recycle_loop_stays_off_when_not_enabled()
     {