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.AbCip.Tests/AbCipDriverWholeUdtReadTests.cs

@@ -35,6 +35,7 @@ public sealed class AbCipDriverWholeUdtReadTests
         ]);
 
     /// <summary>Verifies that multiple members of the same UDT trigger only one parent read.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Two_members_of_same_udt_trigger_one_parent_read()
     {
@@ -55,6 +56,7 @@ public sealed class AbCipDriverWholeUdtReadTests
     }
 
     /// <summary>Verifies that each UDT member is decoded at its correct offset.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Each_member_decodes_at_its_own_offset()
     {
@@ -81,6 +83,7 @@ public sealed class AbCipDriverWholeUdtReadTests
     }
 
     /// <summary>Verifies that parent read failure marks all grouped members as Bad.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Parent_read_failure_stamps_every_grouped_member_Bad()
     {
@@ -101,6 +104,7 @@ public sealed class AbCipDriverWholeUdtReadTests
     }
 
     /// <summary>Verifies that mixed batches group UDT members and fall back to atomic reads.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Mixed_batch_groups_udt_and_falls_back_atomics()
     {
@@ -121,6 +125,7 @@ public sealed class AbCipDriverWholeUdtReadTests
     }
 
     /// <summary>Verifies that a single UDT member uses the per-tag read path rather than grouping.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Single_member_of_Udt_uses_per_tag_read_path()
     {