fix: presence unreliable within same pod

It was broadcasting presence changes to other pods, but not notifying
clients connected to the same pod

go/internal/pusher/hub.go

@@ -101,6 +101,9 @@ func (h *Hub) handleSubscribe(ctx context.Context, req *subscribeRequest) {
 		h.channels[req.channelID] = ch
 	}
 
+	// Capture before addMember so multi-tab joins don't emit a spurious join.
+	wasPresentLocally := ch.hasHumanID(req.conn.humanID)
+
 	// Add to local channel
 	ch.addMember(req.conn, req.conn.humanID)
 
@@ -124,6 +127,16 @@ func (h *Hub) handleSubscribe(ctx context.Context, req *subscribeRequest) {
 		Channel:  req.channelID,
 		Presence: presence,
 	})
+
+	// Notify other local members. The Redis self-filter drops our own echo,
+	// so same-pod peers would otherwise never hear about this join.
+	if !wasPresentLocally {
+		ch.broadcast(ServerMessage{
+			Type:    TypeJoin,
+			Channel: req.channelID,
+			HumanID: req.conn.humanID,
+		}, req.conn)
+	}
 }
 
 func (h *Hub) handleUnsubscribe(ctx context.Context, req *unsubscribeRequest) {
@@ -144,6 +157,16 @@ func (h *Hub) handleUnsubscribe(ctx context.Context, req *unsubscribeRequest) {
 		slog.Error("redis unsubscribe failed", "channelId", req.channelID, "error", err)
 	}
 
+	// Notify other local members iff the humanID is fully gone from this pod
+	// (multi-tab: other conns keep them present, so no leave fires).
+	if !ch.hasHumanID(req.conn.humanID) {
+		ch.broadcast(ServerMessage{
+			Type:    TypeLeave,
+			Channel: req.channelID,
+			HumanID: req.conn.humanID,
+		}, req.conn)
+	}
+
 	// Clean up empty local channel
 	if ch.isEmpty() {
 		delete(h.channels, req.channelID)
@@ -192,6 +215,14 @@ func (h *Hub) handleDisconnect(ctx context.Context, conn *Conn) {
 			slog.Error("redis unsubscribe on disconnect failed", "channelId", channelID, "error", err)
 		}
 
+		if !ch.hasHumanID(conn.humanID) {
+			ch.broadcast(ServerMessage{
+				Type:    TypeLeave,
+				Channel: channelID,
+				HumanID: conn.humanID,
+			}, conn)
+		}
+
 		if ch.isEmpty() {
 			delete(h.channels, channelID)
 		}