Stops fat-fingered early sends. The single-line input is now an auto-growing
textarea (Claude-app style): Enter inserts a newline and expands the box (up to a
cap, then it scrolls); you tap the ↑ arrow to send. ⌘/Ctrl+Enter still sends from
a hardware keyboard. Send button is now a round arrow; box resets to one line
after sending. Mobile button is a 42-44px touch target.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>