feat: add cli contract and local browser events

internal/application/event_bus.go

@@ -0,0 +1,49 @@
+package application
+
+import (
+	"sync"
+
+	"chub/internal/domain"
+)
+
+// EventBus is the in-process local event channel shared by the UI and CLI
+// adapters. Subscribers own cancellation; publishing never blocks a browser
+// process monitor on a slow presentation consumer.
+type EventBus struct {
+	mu      sync.RWMutex
+	nextID  uint64
+	clients map[uint64]chan domain.BrowserEvent
+}
+
+func NewEventBus() *EventBus { return &EventBus{clients: make(map[uint64]chan domain.BrowserEvent)} }
+
+func (b *EventBus) Subscribe(buffer int) (<-chan domain.BrowserEvent, func()) {
+	if buffer < 1 {
+		buffer = 1
+	}
+	b.mu.Lock()
+	b.nextID++
+	id := b.nextID
+	ch := make(chan domain.BrowserEvent, buffer)
+	b.clients[id] = ch
+	b.mu.Unlock()
+	return ch, func() {
+		b.mu.Lock()
+		if existing, ok := b.clients[id]; ok {
+			delete(b.clients, id)
+			close(existing)
+		}
+		b.mu.Unlock()
+	}
+}
+
+func (b *EventBus) Publish(event domain.BrowserEvent) {
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+	for _, ch := range b.clients {
+		select {
+		case ch <- event:
+		default:
+		}
+	}
+}