Disable automatic loading of context.txt into Streamlit sessions

[DavidJBianco]

Motivation

• Prevent accidental disclosure of server-side context.txt into LLM prompts and external providers by avoiding auto-injection into every st.session_state session.

Description

• Replace automatic file read of context.txt in peak_assistant/streamlit/app.py with initializing st.session_state["local_context"] to an empty string and add an inline security note explaining why server-side context is not auto-injected.

Testing

• Compiled peak_assistant/streamlit/app.py and peak_assistant/streamlit/util/runners.py with python -m compileall (success) and ran PYTHONPATH=. pytest -q tests/unit_tests/test_streamlit_helpers_mcp_bugs.py which failed during collection due to a missing python-dotenv dependency in the environment.

---

Codex Task

[DavidJBianco]

Superseded by #86, which cherry-picked this fix. Merged into dev via merge commit 39cb907.