docs: simplify the Catalog overview with a section tour - #3240

Summary

• simplify the Catalog overview to one sentence, a fast visual tour, two entry-point cards, and a three-step usage flow
• add a deterministic 19.25s HyperFrames v3 montage covering all 11 Catalog sections
• embed that montage in a real hyperframes-player with Preview and copyable HTML tabs
• showcase the requested first Captions item, 3D iPhone HTML-in-Canvas item, and Miao's recent ai-chat-reveal addition
• replace the player with a poster when reduced motion is enabled

Verification

• bunx vitest run scripts/catalog-overview-video.test.ts — 3 passed
• bun run check:docs-snippet-motion — passed
• bun run test:scripts — 176 node tests + 29 catalog tests passed
• bunx oxfmt --check ... — passed
• mint validate — passed
• mint broken-links — passed
• npx [email protected] check docs/video-sources/catalog-overview --at-transitions --snapshots — passed; runtime/layout/motion clean, 5/5 contrast checks
• local Mintlify /catalog: real player playback, HTML copy tab, desktop, 390px narrow, dark, and reduced-motion verified; no narrow horizontal overflow
• media: H.264 1920×1080, 60fps, 19.25s, 1,155 frames, silent, full decode clean

Media dependency

The v3 MP4/JPG are intentionally untracked and still need the established scripts/upload-docs-images.sh maintainer upload before merge. The intended immutable URLs currently return 403; local Mintlify proof used those exact generated artifacts through a localhost asset override.

Review proof

The revised v3 video and route screenshots (player, HTML copy, narrow, dark, and reduced-motion) were uploaded to the private review thread.