[Bug]: Mobile: message queued while agent is working is never sent if the app goes to background — only delivered on next app open

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. Start a thread and wait for the agent to be actively working on a turn.
2. Send a follow-up message while the turn is in progress — it gets queued (locally, it seems).
3. Lock the phone or switch to another app.
4. Wait for the agent to finish its turn.

Expected behavior

The queued message is delivered to the agent once the current turn settles, regardless of whether the mobile app is foregrounded. Queuing should be owned by the server/backend, not the client.

Actual behavior

The queued message stays pending indefinitely. It is only actually sent when I reopen the app. If queuing happens client-side, it silently defeats the purpose of queuing on mobile: you queue a follow-up, put your phone away, and come back later to find the agent idle and the message never delivered.

Related

Not a duplicate of #231 / #4550 (those are feature requests for Queue/Steer modes) — this is about delivery reliability of the existing queue behavior when the mobile app is backgrounded.

Start in apps/mobile by tracing how follow-up messages are queued and delivered when the app is backgrounded, then inspect the related backend delivery path. Reproduce the steps with the app backgrounded and verify that a queued message is delivered when the agent turn settles without reopening the app.