feat(demo): scene protocol docs page + SEO pass

[karngyan]

What

Three things in one docs-site pass:

New docs page: /scene-protocol. Documents the scenes system end to end: the SceneManifest format (contiguity rule, trailing-silence semantics, sidecar captions/storyboard), the kino:-namespaced postMessage wire format with a per-message table and the ready→init handshake, trust boundaries on both sides of the iframe (origin + source checks, the document-pip opener case), createSceneHost usage, scene authoring against the SceneClock, and the ScenesPlayer embed. Carries the same copy-as-markdown mirror as the other pages. Route is /scene-protocol rather than /scenes because the static demo scenes.html shadows /scenes in both dev (Vite html resolution) and production (asset html_handling runs before the SPA fallback).

SEO. The SPA served one identical head for every URL — crawlers and link scrapers that don't execute JS never saw per-page meta. Now demo/seo.json is the single source of truth for per-route title/description, consumed twice:

• demo/prerender.ts (new pnpm build:demo = vite build + prerender) stamps title, description, canonical, OG, and Twitter tags into a static HTML copy per route (install.html, scene-protocol.html, …) that the Worker's html handling serves for the clean URL, and emits sitemap.xml. Throws if a tag pattern stops matching.
• usePageMeta in demo/seo.ts keeps the head in sync during client-side navigation and marks the 404 route noindex.

Plus: full default head in index.html (OG/Twitter cards with og.png from the repo banner), robots.txt, real meta on scenes.html, noindex on the scenes-host.html fixture, and a CI step that runs pnpm build:demo so the prerender pass stays exercised.

Film grain removed — film-grain overlay span + its CSS utility are gone.

Why not TanStack Start

A framework migration rewrites the site and the deploy model to fix what is, for a five-page docs site, a head-tags problem. The prerender pass gets crawler-visible per-route meta with zero new dependencies. If full static HTML bodies ever matter, that's the point to revisit SSG/SSR.

Verification

• pnpm format:check, typecheck, lint, test (188) all green; pnpm build:demo output inspected — per-route titles/canonicals and sitemap correct.
• Headless browser: home → Scene protocol → Theming navigation updates title/canonical/og:url per hop; unknown path gets noindex; zero console/page errors; grain element absent.

🤖 Generated with Claude Code

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	kino	dda37af	Commit Preview URL Branch Preview URL	Jul 21 2026, 05:00 PM