[Feature]: Auto-grow the native mobile composer for long prompts

[fionn77]

Before submitting

• I searched existing issues and did not find a native-mobile request for an auto-growing long-prompt composer.
• I am describing a concrete mobile use case.

Area

apps/mobile on Android.

Thanks for continuing to improve the native mobile experience.

Problem or use case

When writing a longer prompt in the Android app, the composer shows only about three lines at a time and then scrolls internally. Reviewing or editing a multi-paragraph prompt becomes awkward because most of the draft is hidden inside a very small text area.

Proposed solution

Let the native composer grow vertically as the prompt wraps onto additional lines.

A practical behavior would be:

• start compact for short prompts;
• expand automatically while the draft grows;
• stop at a sensible maximum, such as a portion of the available viewport;
• only then use internal scrolling;
• keep the send/stop controls reachable above the keyboard;
• preserve the cursor position and draft while resizing.

A manual expand/full-screen drafting action could also be useful, but automatic growth would solve the common case with less friction.

Expected behavior

A longer prompt should expose substantially more than three lines while it is being edited, so the user can review the surrounding paragraphs without constantly scrolling inside the composer.

Environment

• Official T3 Code native Android app
• Google Pixel 7a
• Android OS and app/OTA versions not captured

Related issues

• [Feature]: Collapse chat input box on mobile when not focused #1262 requests collapsing the web composer when it is not focused.
• [Feature]: Collapsible composer so the thread is readable while a question or approval is pending #5120 requests a collapsible web composer around approvals, questions, and long drafts.

Those are compatible ideas but do not cover growing the focused native-mobile editor while composing a long prompt.

I am happy to test the resizing and keyboard behavior on Android.