On latest `dev`, each sidebar section header in `Sidebar/Section.svelte` is a real `<button>` carrying `aria-expanded` and `aria-controls`, but it has **no activation handler**. The toggle comes only from `on:pointerup` on the wrapper inside `common/Collapsible.svelte`.
Keyboard activation dispatches a synthetic `click`, never `pointerup`, and that wrapper's own `on:click` handler calls `stopPropagation()`. So pressing Enter or Space on the header does nothing at all, while `aria-expanded` tells assistive technology this is a working disclosure control.
This affects every section in the sidebar: Models, Notes, Channels, Folders and Chats. Section state is persisted to `localStorage`, so a user whose section was collapsed on a previous visit has no keyboard way to open it again, and the content stays unreachable.
Breaks WCAG 2.1.1 Keyboard (Level A), and 4.1.2 Name, Role, Value (Level A), because the exposed expanded state belongs to a control that cannot be operated.
Fix: handle activation on the header button itself, where focus actually lands, and stop the now duplicate pointer path so a mouse click does not toggle twice. The existing inline `onChange` body is extracted to `setOpen` so the `change` dispatch and the `localStorage` write stay in one place and fire exactly once per toggle in both input modes. The adjacent "+" (`onAdd`) button already stops both `pointerup` and `click`, so it still does not toggle the section.
`Collapsible`'s wrapper cannot simply become a `<button>` instead, because its slot receives buttons from this component and others, so the fix belongs here.
`common/Folder.svelte` and `Sidebar/RecursiveFolder.svelte` have the same latent defect and are not touched by this PR.
Severity: Critical. Sidebar navigation cannot be expanded without a mouse.
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When navigating from a chat to a non-chat route (e.g. the admin panel),
the previously-viewed chat stayed selected in the sidebar and
deleting/archiving it wrongly redirected back to the new-chat page.
Cloning a chat also left the source chat highlighted alongside the new
clone, so two chats appeared selected at once.
Two independent sources kept the stale selection:
- The chatId store was never cleared when the Chat component unmounted,
so $chatId still pointed at the last-viewed chat (this drove the
delete/archive redirect). Clear chatId/chatTitle in Chat's onDestroy.
- The sidebar's optimistic selectedChatId highlight, set on click, was
only cleared on window blur (hence it appeared to fix itself after a
tab switch) and never followed programmatic navigation. Bind it to the
chatId store so it tracks the active chat for leave, delete and clone.
