## What changed
- Add an optional `timeoutMs` parameter to `thread/shellCommand` and propagate it to user shell execution.
- Preserve the one-hour default when the parameter is omitted or `null`, allow longer deadlines, and treat `0` as an immediate timeout.
- Reject negative or otherwise invalid values before execution. Timing out an auxiliary shell command leaves its active turn running.
## Testing
- Cover default, extended, immediate, invalid, standalone, active-turn, and interruption behavior.
GitOrigin-RevId: d72f67793d9766b7383f28d30140270a4a76a495
This PR adds a new `thread/shellCommand` app server API so clients can
implement `!` shell commands. These commands are executed within the
sandbox, and the command text and output are visible to the model.
The internal implementation mirrors the current TUI `!` behavior.
- persist shell command execution as `CommandExecution` thread items,
including source and formatted output metadata
- bridge live and replayed app-server command execution events back into
the existing `tui_app_server` exec rendering path
This PR also wires `tui_app_server` to submit `!` commands through the
new API.
