[Bug]: The collapsed mobile composer shows a disabled send button instead of Stop while a turn runs#29958

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/web

Steps to reproduce

1. Open the web client and narrow the browser below 640px, or use a phone.
2. Start a turn, for example window.t3dev.replay("showcase") in dev.
3. Tap outside the composer so it collapses to the one-line resting row.

Expected behavior

The composer's action button is the red Stop button while the turn runs, as it is at full width and in the expanded composer.

Actual behavior

The collapsed row shows the send arrow, disabled. You can't stop the turn without first tapping into the composer to expand it.

The collapsed row in ChatComposer.tsx renders its own send button and never consults canInterrupt. Its disabled state includes phase === "running", so during a turn it is a dead button. Only ComposerPrimaryActions, the expanded footer, renders Stop.

Impact

Minor bug or occasional failure

Version or commit

main @ 61c3794c

Environment

Web client, 430×932 viewport (iPhone 14 Pro Max preset), Replay (dev) provider.

Screenshots, recordings, or supporting files

Workaround

Tap the composer to expand it. The footer then shows Stop.