[Bug]: Mobile messages return from Pending to the composer on desktop-created threads

Before submitting

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

Area

apps/mobile

Steps to reproduce

1. Create or start a thread from the T3 Code desktop app.
2. Open that existing thread in the mobile client.
3. Type a follow-up message and tap Send.
4. Watch the message state in the mobile UI.

Expected behavior

The message should remain queued/pending until it is accepted, then start a turn in the existing thread.

Actual behavior

The message briefly moves into the Pending state, then leaves Pending and is restored to the composer text box. No message is sent and no turn starts.

This is distinct from #11755: in that issue the Send tap is swallowed before dispatch while the iOS editor is focused. Here the UI visibly enqueues the message into Pending before delivery rolls back and restores the draft. It is also distinct from #7390, where the Send button remains disabled while a stale native draft carries between threads.

The failure has been observed on threads opened from the desktop app. Whether the same rollback occurs for threads created entirely on mobile has not yet been confirmed.

Impact

Major degradation or frequent failure

The affected thread cannot be continued from mobile; the desktop client is required as a workaround.

Version or commit

Not collected.

Environment

T3 Code desktop and mobile clients. Mobile OS, app versions, provider, and connection mode were not collected.

Logs or stack traces

No logs collected. The visible state transition is: composer -> Pending -> composer.

Screenshots, recordings, or supporting files

None collected.

Workaround

Send the follow-up from the desktop app.

Start in apps/mobile by reproducing the composer → Pending → composer transition on a thread created in the desktop app. Trace the rollback after sending and compare it with the expected queued state; done means the message remains pending, is accepted, and starts a turn in the existing thread.