feat(website): add authentic cinematic scroll film

[Natsummerance]

Summary

• Fix showcase capture geometry: ReadMD is captured as the real landscape desktop workbench at 1440x810 logical / 2880x1620 pixels, eliminating the portrait aspect and bottom whitespace on the site.
• Add programmatic pixel QA for dimensions, hashes, tonal range, edge structure, color detail, and blank detection.
• Add a reusable authentic recording pipeline using Playwright's native video recorder; Recordly (22,497 stars) is referenced for composition patterns only.
• Add FFmpeg finalization and 57 WebP scroll frames decoded from the real product recording.
• Upgrade the homepage with semantic particles, staged reveals, parallax, dark-mode support, reduced-motion fallbacks, progress captions, perspective stage, and scroll-driven canvas film.

Approvals

Design / authentic capture / performance release: 9.89 / 9.87 / 9.82; final decision meeting 9.86 (cinematic_experience_approval.json).

Validation

• npm run verify:release: green across 40 canonical URLs and motion contracts.
• Capture pixel audit: 8/8 screenshots at expected 2880x1620, all unique and nonblank.
• Product film audit: 11.433s, 1440x810, five sampled frames unique and nonblank.
• Browser smoke: 40/40 routes passed; film frames ready, scroll reaches frame >=45 of 57, center pixel nonblank.