Summary

• expand the Streamlit sidebar on startup
• persist the selected LLM index in temp/stapp_state.json
• restore the saved LLM before the frontend worker starts
• tolerate UTF-8 BOM if the state file is edited by Windows tools

This covers the sidebar-default and model-selection-memory parts of #200 without adding dependencies.

Testing

• conda env: ga-stapp-verify, Python 3.12, Streamlit 1.57.0
• python -m py_compile frontends\stapp.py agentmain.py llmcore.py
• python -m unittest discover -s tests -v
• launched Streamlit at http://127.0.0.1:18652
• Playwright + Microsoft Edge: verified sidebar aria-expanded=true, width=300
• Playwright: preloaded temp/stapp_state.json with llm_no=1 and verified UI restored verify-secondary
• Playwright: selected verify-primary in the sidebar and verified temp/stapp_state.json updated to llm_no=0