Compare-mode composer (shared-composer.tsx) wraps the send button in
TooltipIconButton without setting aria-label="Send message", so the
playwright_extra_ui Compare step's button[aria-label="Send message"]
selector matched 0 elements and timed out at 30s.
Two changes:
1. Test: switch from clicking the send button to pressing Enter on
the textarea. The composer's onKeyDown handler maps plain Enter
to send(), which is also the natural user flow.
2. Frontend: add aria-label="Send message" to the compare composer's
send button. Single-thread composer (thread.tsx) already sets
this; mirror it for accessibility consistency and to keep the
selector working as a fallback in older builds.
c8b13b7fe2