Python starters were trying to run uvicorn with agent.<module>:app but
those modules don't export a FastAPI app. The demo packages use
agent_server.py as the FastAPI wrapper, so starters need it too.
Changes:
- Copy agent_server.py from each demo package into starter root,
rewriting "from agents." to "from agent." for the starter layout
- Update all non-langgraph Python devScripts to use agent_server:app
- Update Dockerfile.python to COPY agent_server.py for non-langgraph
- Update getEntrypointBlock() generic Python to use agent_server:app
- Make langgraph-fastapi use langgraph_cli dev like langgraph-python
(it was incorrectly configured as a uvicorn-based starter)
- Regenerate all starters