feat(tui): remove /provider alias for /model (#20358)
/model is the canonical command; /provider was a redundant alias that
dispatched to the same ModelPicker overlay. Drop the alias, the regex
branch in useCompletion, and the alias-coverage test.
fix(tui): copilot review on #16707 — naming, label consistency, esc priority
- Rename removeAt → removeAtInPlace and document the mutation
contract; the old name read like a non-mutating helper.
- Hotkey table + queue header: use Ctrl+X / Esc to match the
rest of the UI (was ⌃X / esc).
- Render the queued header as a single template literal so JSX
text-node whitespace can't sneak into the rendered line.
- Make Esc while editing beat the terminal.hasSelection clear:
the header promises 'Esc cancel', so an active selection
shouldn't silently consume the keystroke.