Function toggleCollapse

src/components/CalendarPanel.tsx:130–137

(group: TimeGroup)

  );

  const toggleCollapse = (group: TimeGroup) => {
    setCollapsed((prev) => {
      const next = new Set(prev);
      if (next.has(group)) next.delete(group);
      else next.add(group);
      return next;
    });
  };

  return (
    <div className="font-mono">