Add enhanced XML documentation to MPG generator operation methods (#53473)

* Initial plan

* Add enhanced XML documentation to MPG generator methods

Co-authored-by: live1206 <[email protected]>

* Document XML encoding limitation in code comments

Co-authored-by: live1206 <[email protected]>

* Use XmlDocStatement to build structured XML documentation

Instead of using FormattableString with raw XML tags that get HTML-encoded,
now using XmlDocStatement API to construct structured XML documentation.
This ensures proper XML rendering without encoding issues.

- Created BuildEnhancedXmlDocs method that constructs XmlDocStatement objects
- Builds list with items for Request Path, Operation Id, API Version, and Resource
- Uses XmlDocSummaryStatement to properly wrap the summary content
- XmlDocs.Update() is called to update the summary with structured statements

This addresses the reviewer's feedback to use XmlDocStatement construction.

Co-authored-by: live1206 <[email protected]>

* Regenerate test projects with proper XML documentation

After merging main branch and resolving conflicts, regenerated all test projects
to reflect the updated generator changes. The XML documentation now uses proper
XmlDocStatement construction, resulting in correctly formatted XML tags instead
of HTML-encoded entities.

Generated documentation now properly shows:
- <list type="bullet"> instead of &lt;list type="bullet"&gt;
- <item>, <term>, <description> tags without encoding
- Properly formatted operation metadata (Request Path, Operation Id, API Version, Resource)

Co-authored-by: live1206 <[email protected]>

* Remove dead code and simplify BuildEnhancedXmlDocs

- Removed BuildEnhancedDescription method which was a no-op
- Changed line 87 to use original assignment: _description = description ?? _convenienceMethod.Signature.Description
- Changed BuildEnhancedXmlDocs return type from XmlDocProvider? to void since return value is not used
- Simplified method by directly updating existingXmlDocs instead of returning it

Addresses reviewer feedback to remove redundant code.

Co-authored-by: live1206 <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: live1206 <[email protected]>

Author: Copilot

eng/packages/http-client-csharp-mgmt/generator/Azure.Generator.Management/src/Providers/OperationMethodProviders/ResourceOperationMethodProvider.cs

@@ -18,6 +18,7 @@
 using Microsoft.TypeSpec.Generator.Statements;
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 using static Microsoft.TypeSpec.Generator.Snippets.Snippet;
 
@@ -95,6 +96,65 @@ public ResourceOperationMethodProvider(
             _bodyStatements = BuildBodyStatements();
         }
 
+        /// <summary>
+        /// Builds enhanced XML documentation with structured XmlDocStatement objects for proper XML rendering.
+        /// </summary>
+        private static void BuildEnhancedXmlDocs(InputServiceMethod serviceMethod, FormattableString? baseDescription, TypeProvider enclosingType, XmlDocProvider? existingXmlDocs)
+        {
+            if (existingXmlDocs == null)
+            {
+                return;
+            }
+
+            var operation = serviceMethod.Operation;
+
+            // Build list items for the operation metadata
+            var listItems = new List<XmlDocStatement>();
+
+            // Request Path item
+            listItems.Add(new XmlDocStatement("item", [],
+                new XmlDocStatement("term", [$"Request Path"]),
+                new XmlDocStatement("description", [$"{operation.Path}"])));
+
+            // Operation Id item
+            listItems.Add(new XmlDocStatement("item", [],
+                new XmlDocStatement("term", [$"Operation Id"]),
+                new XmlDocStatement("description", [$"{operation.Name}"])));
+
+            // API Version item (if available)
+            var apiVersionParam = operation.Parameters.FirstOrDefault(p => p.IsApiVersion);
+            if (apiVersionParam != null && apiVersionParam.DefaultValue?.Value != null)
+            {
+                listItems.Add(new XmlDocStatement("item", [],
+                    new XmlDocStatement("term", [$"Default Api Version"]),
+                    new XmlDocStatement("description", [$"{apiVersionParam.DefaultValue.Value}"])));
+            }
+
+            // Resource item (if enclosing type is a ResourceClientProvider)
+            if (enclosingType is ResourceClientProvider resourceClient)
+            {
+                listItems.Add(new XmlDocStatement("item", [],
+                    new XmlDocStatement("term", [$"Resource"]),
+                    new XmlDocStatement("description", [$"{resourceClient.Type:C}"])));
+            }
+
+            // Create the list statement
+            var listStatement = new XmlDocStatement($"<list type=\"bullet\">", $"</list>", [], innerStatements: listItems.ToArray());
+
+            // Build the complete summary with base description and metadata list
+            var summaryContent = new List<FormattableString>();
+            if (baseDescription != null)
+            {
+                summaryContent.Add(baseDescription);
+            }
+
+            // Create summary statement with the list as inner content
+            var summaryStatement = new XmlDocSummaryStatement(summaryContent, listStatement);
+
+            // Update the XmlDocs with the new summary
+            existingXmlDocs.Update(summary: summaryStatement);
+        }
+
         private static void InitializeLroFlags(
             in InputServiceMethod serviceMethod,
             in bool forceLro,
@@ -131,10 +191,19 @@ protected virtual CSharpType BuildReturnType()
 
         public static implicit operator MethodProvider(ResourceOperationMethodProvider resourceOperationMethodProvider)
         {
-            return new MethodProvider(
+            var methodProvider = new MethodProvider(
                 resourceOperationMethodProvider._signature,
                 resourceOperationMethodProvider._bodyStatements,
                 resourceOperationMethodProvider._enclosingType);
+
+            // Add enhanced XML documentation with structured tags
+            BuildEnhancedXmlDocs(
+                resourceOperationMethodProvider._serviceMethod,
+                resourceOperationMethodProvider._convenienceMethod.Signature.Description,
+                resourceOperationMethodProvider._enclosingType,
+                methodProvider.XmlDocs);
+
+            return methodProvider;
         }
 
         protected virtual MethodBodyStatement[] BuildBodyStatements()