Bundle Python backend and MCP bridge in desktop releases

[luckeyfaraday]

Summary

• build a self-contained PyInstaller runtime on Linux, Windows, and macOS and package it with each desktop release
• make packaged Athena launch the bundled FastAPI backend by default while preserving CONTEXT_WORKSPACE_PYTHON as an explicit development override
• launch the context_workspace MCP bridge from the same bundle for Codex, Claude, OpenCode, and Athena Code instead of requiring host Python packages
• route packaged recall refreshes through the bundled runtime and preserve stderr when backend startup fails
• build and health-check the frozen backend and complete a JSON-RPC MCP initialize handshake in PR and release CI

Closes #191

Testing

• python -m pytest — 211 passed
• npm run test:electron — 227 passed
• npm run test:chat — 31 passed
• npm run test:regression — 72 passed
• built the Linux runtime and passed /health with Python removed from PATH and PYTHONPATH
• completed the MCP JSON-RPC initialize handshake from the frozen runtime with host Python unavailable
• built and extracted ATHENA-0.1.12.AppImage, then repeated both the backend health check and MCP handshake using the executable inside the AppImage
• ran the bundled recall-refresh path without host Python packages

Regression protection

• Packaged backend and MCP command selection have Electron regression coverage, including Windows paths.
• The frozen Python launcher, MCP mode, and recall-refresh mode have Python coverage.
• CI builds the actual frozen runtime and requires both a live backend health check and MCP initialize handshake before packaging.