- Nothing selected: z toggles zen (hide both panels)
- Item selected: z expands peek to full width (focus mode)
- z again or Esc exits focus mode and deselects
- j/k still cycle items while in focus mode
- Drag handles between rail/center and center/peek
- Rail: 120–360px range, peek: 250–700px range
- Widths persisted in localStorage
- Handles hidden when panel is collapsed (zen mode)
- Transition disabled during drag for smooth resize