## Why
Configuration and app-server initialization can take time before the main TUI is ready, leaving users unable to begin drafting a prompt.
## What changed
- Show a provisional composer while startup work runs and carry its text, cursor position, paste state, and attachments into the initialized chat.
- Limit the provisional composer to safe editing and cancellation, and quarantine input around session pickers, approvals, and other actionable startup screens.
- Preserve configuration validation before terminal checks and recover terminal state cleanly from startup failures and caught panics.
## Testing
- Cover startup editing, multiline and large pastes, keymaps, cancellation, session-picker handoff, approval boundaries, and draft restoration.
- Verify non-interactive launches report configuration errors before terminal errors.
GitOrigin-RevId: fe04a85cfbbcff21ff87fa81fd17474827858575
a0bed4be21