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)

cli.py

@@ -393,7 +393,7 @@ if click is not None:
         sys.path.insert(0, ".")
         import asyncio
 
-        from mcp_production import main
+        from pry_mcp import main
 
         asyncio.run(main())