[python] Fix output folder of models when output folder is different with namespace in configuration (#5739)

Supplementation for #5711. The
issue is not covered by test case since test case doesn't contain
`models`. Here is updated test case to cover this issue:
https://github.com/Azure/autorest.python/pull/3030/files#diff-5fa7ea68bc2d31e09e995e5f522a9e4f58572767f393937a1cf6baf35fa16664

Author: msyyc

.chronus/changes/fix-namespace-new-2025-0-24-16-11-9.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-client-python"
+---
+
+Fix output folder of models when output folder is different with namespace in configuration

packages/http-client-python/CHANGELOG.md

@@ -1,5 +1,11 @@
 # Change Log - @typespec/http-client-python
 
+## 0.6.9
+
+### Bug Fixes
+
+- Fix output folder of models when output folder is different with namespace in configuration
+
 ## 0.6.8
 
 ### Bug Fixes

packages/http-client-python/generator/pygen/codegen/serializers/__init__.py

@@ -238,7 +238,7 @@ def _serialize_and_write_models_folder(
         self, env: Environment, namespace: str, models: List[ModelType], enums: List[EnumType]
     ) -> None:
         # Write the models folder
-        models_path = self.exec_path(namespace + ".models")
+        models_path = self.exec_path(namespace) / "models"
         serializer = DpgModelSerializer if self.code_model.options["models_mode"] == "dpg" else MsrestModelSerializer
         if self.code_model.has_non_json_models(models):
             self.write_file(

packages/http-client-python/package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@typespec/http-client-python",
-  "version": "0.6.8",
+  "version": "0.6.9",
   "author": "Microsoft Corporation",
   "description": "TypeSpec emitter for Python SDKs",
   "homepage": "https://typespec.io",