Sidebar Dropdown Should Toggle When Clicking an Already-Selected Item

When a user selects a sidebar item with nested routes, the dropdown expands as expected. However, clicking the same selected item again does nothing, even though users naturally expect it to collapse. This leads to:

Reduced control over sidebar visibility

Unnecessary scrolling when sections cannot be collapsed

Lower consistency with typical documentation UI behavior

Expected Behavior

Clicking an already-selected sidebar item should toggle the visibility of its dropdown.

Clicking a non-selected item behaves normally (navigate + expand).

When navigating away, the collapsed state should reset automatically so the correct item appears expanded by default.

首先在 React 文档网站中找到侧边栏项和嵌套下拉菜单的实现，然后复现选中项和未选中项的行为。验证点击选中项会折叠其下拉菜单，导航仍会展开正确的项，并且导航离开后会重置折叠状态。