DOM-free SlideshowController (discrete nav, fragment holds, branch stack)
driving the existing player; <hyperframes-slideshow> web component with a
unified mute+nav capsule (conditional prev/next), floating hotspot overlays,
presenter mode (BroadcastChannel), keyboard/touch, and a scenes getter fed
via the runtime message handler.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
