feat: add elevated bash mode

docs/background-process.md

@@ -16,6 +16,7 @@ Key parameters:
 - `yieldMs` (default 10000): auto‑background after this delay
 - `background` (bool): background immediately
 - `timeout` (seconds, default 1800): kill the process after this timeout
+- `elevated` (bool): run on host if elevated mode is enabled/allowed
 - Need a real TTY? Use the tmux skill.
 - `workdir`, `env`