Present a presentation (the click-through runtime)

Clicking "Present" opens the runtime at /present/:id — a chromeless, full-screen player in its own tab. It flattens every deck slide and every webpage section into one ordered run and plays them straight through.

Advancing:
• Click anywhere, or press → / Space / Page Down to go forward; ← / Page Up to go back; Esc to exit (it closes the tab).
• On a slide with per-element animations, each forward press plays the next animation step, then moves on to the next frame — exactly like a deck's Presenter Mode, preserved across the stitched show. The chip in the bottom-left shows your position (e.g. 7 / 24) and the animation step (✦ 2 / 3).

Webpage sections:
• A webpage section fills the screen in an embedded frame. The label shows in the bottom bar.
• If a section comes up blank, that site blocks being embedded (its X-Frame-Options). Use the "Open ↗" control in the bottom-right to open it in a new tab instead.

The bottom-right controls give you Prev / Next, the Follow-along toggle (see "Follow-along"), and Exit. The runtime requests true full-screen on open; pressing Esc exits both full-screen and the tab.