fix(clients): Present legacy wakes as notifications#17

What Changed

Thread history from earlier V2 orchestrator builds recorded background-command, background-task and delegated-task completions as agent-authored user messages. Web and mobile now show those entries as notification cards, "Background task finished" or "Delegated task finished" with a count when several finished together, and keep the original text as the detail. Stored data is not changed.

Messages that are already typed notifications, or that were sent by another thread, are left as they are.

Why

Old wakes looked like messages the user had typed, which made existing threads confusing to read next to newer threads that already show notifications.

UI Changes

Affected history entries render as notification cards instead of user messages. No screenshots are attached.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes