feat(desktop): composer queue — queue many, edit/delete/cancel-edit, Cursor-style

Press Enter while busy with a draft to queue it; with no draft to interrupt
and send the next queued turn. Auto-drains one queued turn each time the
session settles, same as Cursor. Queue persists across reloads so an
interrupted-and-queued turn isn't lost on refresh.

Each queued row supports edit-in-composer (with explicit Save/Cancel),
send-now (↑), and delete. Drain skips only the entry currently being
edited so the rest of the queue keeps flowing.

Queue dequeue is transactional — an entry only leaves the queue after
`prompt.submit` is accepted, so a rejected submit doesn't drop the turn.

Also shrinks the `[interrupted]` marker to a muted one-liner and drops
its assistant footer so it stops looking like a real reply.

apps/desktop/src/app/desktop-controller.tsx

@@ -470,7 +470,7 @@ export function DesktopController() {
       onAttachDroppedItems={composer.attachDroppedItems}
       onAttachImageBlob={composer.attachImageBlob}
       onBranchInNewChat={messageId => void branchInNewChat(messageId)}
-      onCancel={() => void cancelRun()}
+      onCancel={cancelRun}
       onDeleteSelectedSession={() => {
         if (selectedStoredSessionId) {
           void removeSession(selectedStoredSessionId)