server: fix event dropping - use blocking callback instead of TrySend

The pubsub library's SubscribeChan uses non-blocking TrySend which
drops events when the channel is full. Switch to Subscribe with a
blocking callback to ensure no events are lost.

Also increased channel buffers from 64 to 256.

cmd/olliesrv/internal/session/event.go

@@ -31,9 +31,16 @@ func PublishEvent(topic, payload string) {
 }
 
 // SubscribeEvents returns a channel that receives all events matching the topic.
+// Events are never dropped — publishing blocks if the channel is full.
 func SubscribeEvents(ctx context.Context, topic string) <-chan Event {
-	ch := make(chan Event, 64)
-	sub := eventBus.SubscribeChan(topic, ch, pubsub.KeepOpen)
+	// Use a callback instead of SubscribeChan to avoid non-blocking TrySend
+	ch := make(chan Event, 256)
+	sub := eventBus.Subscribe(topic, func(ev Event) {
+		select {
+		case ch <- ev:
+		case <-ctx.Done():
+		}
+	})
 	go func() {
 		<-ctx.Done()
 		eventBus.Unsubscribe(sub)
@@ -48,7 +55,7 @@ func SubscribeEvents(ctx context.Context, topic string) <-chan Event {
 func SubscribeEventsFiltered(ctx context.Context, filter string) <-chan Event {
 	// Subscribe to all events and filter client-side for complex patterns
 	// (pubsub only supports simple topic matching)
-	ch := make(chan Event, 64)
+	ch := make(chan Event, 256)
 	allEvents := SubscribeEvents(ctx, "*")
 	go func() {
 		defer close(ch)
@@ -56,7 +63,8 @@ func SubscribeEventsFiltered(ctx context.Context, filter string) <-chan Event {
 			if MatchTopic(filter, ev.Topic) {
 				select {
 				case ch <- ev:
-				default: // drop if full
+				case <-ctx.Done():
+					return
 				}
 			}
 		}