[Feature Request] Setting to position prompt input at top of terminal

Summary

Add a settings.json option to render the prompt input box at the top of the terminal instead of the bottom.

Motivation

• On wide/tall terminal windows, the active input sits far from where the eye tracks recent output, especially after long streamed responses.
• Some users prefer top-anchored input (matches certain chat clients, IDE panels, and tmux configurations).
• Pairs naturally with tui: "fullscreen" — where the alt-screen already lets Claude Code own the layout.

Proposed API

A new key in settings.json:

{
  "inputPosition": "top"
}

Values: "bottom" (default, current behavior) | "top".

Alternatively, a slash command toggle: /input-position top|bottom.

Alternatives considered

• tui: "fullscreen" — changes renderer mode but input remains at the bottom.
• viewMode — affects transcript display, not input location.
• Terminal-level workarounds (tmux pane flipping) — fragile and don't survive resizes.

Related issues

None found searching for "input position" / "prompt at top" in this repo.