Add expose_port previews with a Preview tab; leave setup to AGENTS.md

internal/server/server.go

@@ -83,6 +83,7 @@ func (s *Server) publish(ev api.Event) {
 	s.agents.Observe(ev)
 	if (ev.Kind == "task.merged" || ev.Kind == "task.discarded") && ev.TaskId != nil {
 		s.terminals.close(*ev.TaskId)
+		go s.agents.Unexpose(context.Background(), *ev.TaskId)
 	}
 }
 
@@ -535,6 +536,21 @@ func (s *Server) ListSnapshots(w http.ResponseWriter, r *http.Request, taskID st
 	writeJSON(w, http.StatusOK, snaps)
 }
 
+func (s *Server) ListPreviews(w http.ResponseWriter, r *http.Request, taskID string) {
+	_, err := s.store.GetTask(r.Context(), taskID)
+	if err != nil {
+		writeStoreError(w, err)
+		return
+	}
+
+	previews, err := s.store.ListPreviews(r.Context(), taskID)
+	if err != nil {
+		writeStoreError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, previews)
+}
+
 func (s *Server) ForkSnapshot(w http.ResponseWriter, r *http.Request, taskID string, n int) {
 	t, p, ok := s.activeTask(w, r, taskID)
 	if !ok {