Add 16 missing members to IWorkerClient (IsReconnecting, WorkerLogReceivedEvent,
PrimeFired, LastApproveTarget, Refresh/RestoreDefaultAgents, UpdateAppSettings,
prime schedule CRUD, UpdateList/UpdateListConfig, all worktree ops).
Switch all production consumers off the concrete WorkerClient type; only
Program.cs/App host still resolves the concrete registration.
Update StubWorkerClient and FakeWorkerClient to satisfy the expanded interface.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
