Daemon push notifications (replace 2s polling with real-time events)

[CKGrafico]

Problem

The TUI polls the daemon every 2s for loop status changes. This means up to 2s latency for status updates, wasted work when nothing changes, and no real-time feel. The daemon already knows when state changes - it just doesn't tell connected clients.

Solution

Add a push/subscribe mechanism: daemon pushes state changes to connected clients in real-time. TUI subscribes instead of polling.

Architecture

Current:
TUI -> every 2s -> GET /list -> daemon returns all loops

Proposed:
TUI -> subscribe once -> daemon pushes diffs on state change
TUI -> every 10s -> GET /list (fallback sync, handles missed pushes)

IPC protocol extension

New request type: subscribe
{"type": "subscribe"}

Daemon tracks subscribed sockets. On any state change (loop started, paused, completed run, etc.), daemon pushes:
{"type": "event", "event": "loop-updated", "data": {...loopMeta}}

Event types:
- loop-updated (status, runCount, lastExitCode changed)
- loop-created
- loop-deleted
- config-reloaded (from hot-reload, issue #10)

Benefits

• Real-time status updates (no 2s delay)
• Less work when idle (no polling)
• Hot-reload changes pushed to TUI instantly
• Feels like a live dashboard, not a polling app

Backward compatibility

• Subscribe is optional - old clients still work with polling
• TUI keeps a 10s fallback poll as safety net
• No breaking changes to existing IPC protocol

Acceptance criteria

• New IPC request type: subscribe
• Daemon tracks subscribed sockets
• Daemon pushes events on state changes
• TUI subscribes on connect, keeps 10s fallback poll
• Event types: loop-updated, loop-created, loop-deleted, config-reloaded
• Works alongside existing polling (backward compatible)
• TUI feels real-time (status changes appear instantly)

Part of v2.0.0 epic #4

[CKGrafico]

Push notification infrastructure implemented. subscribe IPC type, IpcServer.pushEvent(), event response type. Backward compatible with polling. Closed.