Live per-project queue updates via a control event

[Eyalm321]

Type: AFK

What to build

Replace the GUI's queue polling with push updates. Add a coalesced queue-changed event to the control server's event stream (fired when tasks are enqueued/claimed/acked/nacked) plus a queue summary in the read model, and have the GUI subscribe via the existing /events websocket so the sidebar badges/lanes update immediately instead of on a poll timer.

Acceptance criteria

• The control event stream emits a coalesced queue-changed event on task-state mutations
• The GUI updates project badges/lanes from the event instead of polling
• Coalescing prevents event storms under rapid enqueue/claim
• Falls back gracefully if the event stream drops (reconnect/refresh)

Blocked by

• Per-project task count badge in the sidebar (queue↔project keystone) #6