Certify G6 adapter coexistence

[terrizoaguimor]

Stack

Depends on #4 (codex/g5-repository-distribution). Review only the G6 delta.

G6 — adapters and coexistence

• adds a hash-bound 21-project corpus: 7 HTML, 7 Vite production builds, and 7 PliegoRS rendered-output contracts
• certifies pinned Tailwind 3.4.19 and 4.3.3 source inventory and emitted CSS audit
• applies manifest-authorized complete-class-group migrations while Tailwind stays loaded
• proves DOM, ARIA, 49 computed properties, geometry, and exact byte rollback
• adds a clean exact-source Chromium matrix for Windows x64, Linux x64, and macOS arm64
• binds the matrix to a separate pinned PliegoRS SSG/resumability browser artifact
• expands Tailwind inventory to bounded v3 @tailwind layer directives
• records the G6 architecture, maturity boundary, and unchanged RC.2 blockers

Local verification

• pnpm check:adapter-coexistence-authority
• pnpm check:adapter-coexistence -- --browser=chromium — 21/21 passed on Windows
• cargo +1.96.0 test --locked -p pliego-css-source — 53 unit + 12 migration tests passed
• cargo +1.96.0 clippy --locked -p pliego-css-source --all-targets -- -D warnings
• pnpm check:release-authority
• pnpm check:docs — 206 Markdown files / 522 local links
• pnpm check:maturity
• pnpm check:representative-gaps
• pnpm 11.7 frozen lockfile replay

The hosted adapter workflow is required for promotion. Immutable Releases is enabled at the repository level, but this PR creates no tag or release.

[terrizoaguimor]

Hosted G6 certification is green on exact PR source:

• Adapter coexistence workflow: https://github.com/celiumsai/pliegocss/actions/runs/29968630130
• Windows x64 Chromium: 21/21 projects
• Linux x64 Chromium: 21/21 projects
• macOS arm64 Chromium: 21/21 projects
• Aggregate matrix: 3 hosts × 21 projects = 63 exact-source replays
• Pinned PliegoRS SSG/WASM/resumability browser gate: passed
• CI, existing 3×3 browser/output certification, and repository distribution workflows: passed
• Immutable Releases: enabled at repository scope

No tag or release was created. RC.2 remains blocked under the existing release authority.