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/AbCipDriverTests.cs

@@ -19,6 +19,7 @@ public sealed class AbCipDriverTests
     }
 
     /// <summary>Verifies InitializeAsync with no devices succeeds and marks driver healthy.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task InitializeAsync_with_empty_devices_succeeds_and_marks_healthy()
     {
@@ -28,6 +29,7 @@ public sealed class AbCipDriverTests
     }
 
     /// <summary>Verifies InitializeAsync registers devices with their respective PLC family profiles.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task InitializeAsync_registers_each_device_with_its_family_profile()
     {
@@ -48,6 +50,7 @@ public sealed class AbCipDriverTests
     }
 
     /// <summary>Verifies InitializeAsync rejects malformed host addresses and faults the driver.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task InitializeAsync_with_malformed_host_address_faults()
     {
@@ -62,6 +65,7 @@ public sealed class AbCipDriverTests
     }
 
     /// <summary>Verifies ShutdownAsync clears devices and marks driver state unknown.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ShutdownAsync_clears_devices_and_marks_unknown()
     {
@@ -79,6 +83,7 @@ public sealed class AbCipDriverTests
     }
 
     /// <summary>Verifies ReinitializeAsync stops and restarts all devices.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task ReinitializeAsync_cycles_devices()
     {