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/Client/ZB.MOM.WW.OtOpcUa.Client.UI.Tests/BrowseTreeViewModelTests.cs

@@ -30,6 +30,7 @@ public class BrowseTreeViewModelTests
     }
 
     /// <summary>Verifies that LoadRootsAsync populates root nodes.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task LoadRootsAsync_PopulatesRootNodes()
     {
@@ -41,6 +42,7 @@ public class BrowseTreeViewModelTests
     }
 
     /// <summary>Verifies that LoadRootsAsync browses with null parent.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task LoadRootsAsync_BrowsesWithNullParent()
     {
@@ -61,6 +63,7 @@ public class BrowseTreeViewModelTests
     }
 
     /// <summary>Verifies that nodes with children have a placeholder.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task LoadRootsAsync_NodeWithChildren_HasPlaceholder()
     {
@@ -73,6 +76,7 @@ public class BrowseTreeViewModelTests
     }
 
     /// <summary>Verifies that nodes without children have no placeholder.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task LoadRootsAsync_NodeWithoutChildren_HasNoPlaceholder()
     {
@@ -84,6 +88,7 @@ public class BrowseTreeViewModelTests
     }
 
     /// <summary>Verifies that first tree node expand triggers child browse.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task TreeNode_FirstExpand_TriggersChildBrowse()
     {
@@ -114,6 +119,7 @@ public class BrowseTreeViewModelTests
     }
 
     /// <summary>Verifies that second tree node expand does not browse again.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task TreeNode_SecondExpand_DoesNotBrowseAgain()
     {
@@ -143,6 +149,7 @@ public class BrowseTreeViewModelTests
     }
 
     /// <summary>Verifies that IsLoading transitions during browse.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task TreeNode_IsLoading_TransitionsDuringBrowse()
     {