Skill/snippet/command/file-mention autocomplete branches in ChatInput
called preventDefault()+return but not stopPropagation(). The Tab key
bubbled to the global window keydown listener in useKeyboardShortcuts,
whose cycle_agent shortcut (default 'tab') then ran setAgent().
Add e.stopPropagation() to all four autocomplete branches so the
synthetic event no longer reaches the window-level handler when an
autocomplete consumes the key.
Quat3rnion
5a2781f970