Mobile: apply a thread's permissions pick right away, not on the next message #72

Follow-up to #70, which fixed this on web and desktop.

Problem

On mobile, changing a thread's Permissions (runtime mode) only writes the composer draft. The real thread.runtime-mode.set is sent only when the next message is delivered:

• apps/mobile/src/features/threads/ThreadSettingsSheet.tsx (onUpdateRuntimeMode)
• apps/mobile/src/features/threads/ThreadRouteScreen.tsx (composer.runtimeMode ?? selectedThread.runtimeMode)
• apps/mobile/src/state/threadOutboxDelivery.ts, which sets the mode before dispatching each queued message

This causes three problems:

• An idle thread can't change mode without posting into it. For a thread like the Jarvis inbox, posting wakes another agent.
• The UI shows a mode the server does not have.
• A message queued during a run sends the mode change mid-run.

What #70 changed on the server

• An owner's thread.runtime-mode.set to the thread's current mode is now a no-op: no event, and no session detach.
• An owner's change is now refused while a run is active, if it would detach a live session (for example Claude). Mobile outbox delivery that sets a different mode mid-run on a Claude thread now gets this refusal, where before the run was ended.

Wanted (match web)

• On an idle server thread, send thread.runtime-mode.set as soon as the user picks.
• Hold the pick until the thread shell shows it, and don't save it in the draft.
• On refusal, show the server's reason and reset the control.
• While a run is active, refuse in the client.
• Stop setting the mode at message delivery.

See apps/web/src/components/chat/useApplyThreadRuntimeMode.ts and useComposerSelection.ts in #70.