Add enhanced XML documentation to MPG generator Get methods in Mockable extensions (#53549)

* Initial plan

* Add enhanced XML documentation to MPG generator Get methods

- Updated MockableResourceProvider.BuildGetMethod to copy XML documentation
- Get methods in Mockable extension classes now include detailed documentation
- Documentation includes Request Path, Operation Id, and Default Api Version
- All test projects regenerated and verified

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

* Add enhanced XML documentation to singleton resource getter methods

- Updated MockableResourceProvider to copy XmlDocs from singleton resource Get methods
- Singleton getters like GetFooSettings() now include detailed documentation
- Documentation includes Request Path, Operation Id, Default Api Version, and Resource

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/MockableResourceProvider.cs

@@ -233,10 +233,19 @@ private IEnumerable<MethodProvider> BuildMethodsForResource(ResourceClientProvid
                         resource.Type,
                         This.As<ArmResource>().Client(),
                         BuildSingletonResourceIdentifier(This.As<ArmResource>().Id(), resource.ResourceTypeValue, resource.SingletonResourceName!)));
-                yield return new MethodProvider(
+                var method = new MethodProvider(
                     resourceMethodSignature,
                     bodyStatement,
                     this);
+
+                // Copy the enhanced XML documentation from the singleton resource's Get method if available
+                var getMethod = resource.Methods.FirstOrDefault(m => m.Signature.Name == "Get");
+                if (getMethod?.XmlDocs?.Summary != null)
+                {
+                    method.XmlDocs?.Update(summary: getMethod.XmlDocs.Summary);
+                }
+
+                yield return method;
             }
             else
             {
@@ -278,11 +287,19 @@ static MethodProvider BuildGetMethod(TypeProvider enclosingType, MethodProvider
                         [.. pathParameters, .. resourceGetMethod.Signature.Parameters],
                         Attributes: [new AttributeStatement(typeof(ForwardsClientCallsAttribute))]);
 
-                    return new MethodProvider(
+                    var method = new MethodProvider(
                         signature,
                         // invoke on a MethodSignature would handle the async extra calls and keyword automatically
                         Return(This.Invoke(collectionGetSignature).Invoke(resourceGetMethod.Signature)),
                         enclosingType);
+
+                    // Copy the enhanced XML documentation from the collection's Get method
+                    if (resourceGetMethod.XmlDocs?.Summary != null)
+                    {
+                        method.XmlDocs?.Update(summary: resourceGetMethod.XmlDocs.Summary);
+                    }
+
+                    return method;
                 }
             }
         }