v0.3.9 — Docker Alpha Visibility

This bridge release makes the current v0.4 Docker work visible without overclaiming isolated mode as done.\n\nHighlights:\n- Added execution-path visibility in the dashboard and supervisor snapshot: Host, Isolated Alpha, or Host Fallback\n- Emitted explicit isolated-worker status events so Docker attempts are visible in live runs\n- Clarified in the docs that the Docker isolation architecture is built and integrated\n- Kept host fallback as the safe behavior when Claude subscription auth is unavailable inside containers\n\nCurrent status:\n- Supervisor workflow works\n- Fast mode works\n- Strict mode works\n- Docker/isolation architecture is built but still alpha\n- Full public isolated mode is still blocked by unreliable Claude subscription auth in containers