feat(ssr): extract shared Astro CSS

[tenphi]

Summary

• add opt-in shared CSS extraction to the Astro integration via css: { mode: 'extract' }
• expose ordered collector artifacts and preserve page-local CSS and cascade order
• support every collector artifact kind: property, font-face, counter-style, function, raw, global, chunk, and keyframes
• emit deterministic content-hashed assets with Astro base and build.assets support
• preserve CSP nonces on extracted links and recognize link-only SSR output during client global-style deduplication
• add unit coverage plus an Astro production-build fixture for zero-client-JS static pages
• document the integration and include a minor changeset

Verification

• pnpm typecheck
• pnpm lint
• pnpm format
• pnpm format:check
• pnpm build
• pnpm size
• pnpm test (79 files, 2,128 tests)
• pnpm check:test-only
• pnpm knip
• production fixture extracts all eight artifact kinds and keeps a route-only keyframe inline
• production-tested on all 8 tenphi.me routes: identical selected computed styles, pseudo-elements, geometry, text, and element counts across 4,043 elements; no console errors
• tenphi.me payload comparison: 29.1% less raw HTML+CSS and 14.1% less gzip than inline delivery

[github-actions]

📦 Snapshot release

Published 0.0.0-snapshot.94a5096.

pnpm add @tenphi/tasty@0.0.0-snapshot.94a5096