Unify GitHub Pages site

[PatrickJS]

Summary

• Replace the README-only Pages builder with the shared Async Pages shell.
• Publish README plus templates into .async/pages through docs.site.
• Keep the dispatch footer pointed at pipeline.js.

Verification

• pnpm run pipeline:task:docs.site
• pnpm run pipeline:sync:check && pnpm run pipeline:github:check
• pnpm run pipeline:verify:force
• local Chrome/Playwright visual smoke covered the dispatch shared Pages layout

[github-actions]

Preview package

Preview for PR head 4c77e309b2934e42ba863d2942df030dcca57da8 (built from its merge with main), published to GitHub Packages as @async/dispatch.

Latest successful build for this PR:

pnpm add @async/dispatch@pr-2

Exact commit build:

pnpm add @async/dispatch@0.0.0-pr.2.sha.4c77e309b2934e42ba863d2942df030dcca57da8

Requires GitHub Packages auth and @async:registry=https://npm.pkg.github.com in your npm config.