6285eeb6c0
Implements all 6 critical resilience fixes from phase-a-stop-dying.md: - Issue 2.9: Migrate std::sync::RwLock → parking_lot::RwLock (7 files) Prevents lock poisoning cascade on writer panic - Issue 2.2: Add install_panic_hook() to log panics via tracing Ensures panics are captured in logs/journald before process death - Issue 3.7: Add ExecStopPost to systemd service Cleans up stale FUSE mounts on service stop - Issue 2.7: Add check_stale_mount() detection on startup Auto-cleans leftover mounts from previous crashes - Issue 2.10: Integrate sd_notify for systemd lifecycle Sends READY=1 after mount, STOPPING on shutdown - Issue 2.1: Add signal handling with spawn_mount Catches SIGTERM/SIGINT for clean shutdown instead of instant death All 7 Phase A tests pass: - test_poisoned_tree_lock_returns_eio_not_panic - test_parking_lot_rwlock_survives_panic - test_panic_hook_logs_to_tracing - test_systemd_service_has_execstoppost - test_stale_mount_check_function_exists - test_sd_notify_ready_sent - test_sigterm_triggers_shutdown