feat(demo): expand video to show flyout + free-travel triangle

Extends the 10s composition to 14.5s, adding the second hero feature:
the safe diagonal-travel zone for cascading flyouts.

Three scenes with crossfade transitions:
1. Title (0-2.5s)
2. Menu interaction (2.3-12.5s) — three beats:
   a. Cursor (now a proper NW arrow pointer, not a dot) descends
      to Insert; fisheye expansion fires.
   b. Flyout slides out from Insert with four submenu items.
      Caption swaps from "Items expand" to "Flyouts stay open
      on the diagonal."
   c. Coral dashed safe-zone triangle fades in (apex at cursor
      tip, base on flyout's left edge). Cursor travels diagonally
      to Table — Format and Help stay quiet, Insert stays purple,
      flyout persists. The triangle teaches *why*.
3. CTA (12.3-14.5s)

Triangle z-indexed above the menu so the wedge is visible across
the parent items (otherwise hidden behind the opaque menu panel).

580KB MP4. Composition source remains reproducible — re-render via
`cd demo-video && npx hyperframes render`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: andyed