refactor(mcp): modernize imports to use pry_mcp sub-package directly

- api.py, cli.py, mcp_sse.py now import from pry_mcp

- tests import from pry_mcp (snapshot tests still verify mcp_production shim)

mcp_sse.py

@@ -29,7 +29,7 @@ from typing import Any
 from fastapi import HTTPException, Request, Response
 from fastapi.responses import StreamingResponse
 
-from mcp_production import (
+from pry_mcp import (
     register_mcp_notification_observer,
     unregister_mcp_notification_observer,
 )