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 文件網站中找到側邊欄項目和巢狀下拉選單的實作，然後重現已選取和未選取項目的行為。驗證點擊已選取的項目會收合其下拉選單、導覽仍會展開正確的項目，以及導覽離開後會重設收合狀態。