feat(sync-ui): defer app quit until async cleanup resolves

- check-host participates in active-run coordination and can be cancelled
- shutdown() cancels and awaits the active launcher run on quit
- onWillQuit calls preventDefault and re-triggers quit once cleanup settles
- Snapshot mode awaits tracker quiescent before writing output
- Auto-scheduler catches synchronous triggerHostSync failures
- SCP endpoint accepts Windows absolute paths; cmd.exe rejects % in quoted values
- runAppCommand unified (inherit vs pipe stdio) in launcher/mpv.ts
- Docs: add --check, --json, --ui, --sync-cli, --make-temp/--remove-temp examples

docs-site/launcher-script.md

@@ -114,6 +114,8 @@ Unfinished sessions (a crash mid-playback) are skipped until the app finalizes t
 
 `subminer sync <host> --check` verifies a host without touching any data: it probes the SSH connection, locates SubMiner on the remote (launcher or app binary), and reports its version. `--json` switches any sync mode to machine-readable NDJSON progress output (this is what the sync window consumes).
 
+`sync --make-temp` creates a restricted temporary directory and prints its path; `sync --remove-temp <dir>` removes one created by that command. They are internal SSH transfer helpers, exposed for compatibility but normally invoked only by sync itself. `SubMiner --sync-cli sync ...` is the packaged app's headless compatibility entrypoint; use `SubMiner --sync-cli --help` for its sync-specific help. The `subminer sync` launcher command selects this entrypoint automatically.
+
 ### Sync window
 
 `subminer sync --ui` (or **Sync Stats & History** in the tray menu) opens a dedicated window for the same engine: