fix: serve docs as static Cloudflare assets

[regenrek]

Summary

• export every human and agent-readable docs route as a direct Cloudflare asset
• move Fumadocs search to a build-time Orama index and preserve Markdown, redirects, headers, sitemap, and custom 404 behavior
• replace the OpenNext Worker deployment gate with a complete static artifact and Wrangler dry-run gate

Why

The production Cloudflare account enforces a 10 ms Worker CPU limit. Live traces showed cold OpenNext requests ending with outcome: exceededCpu, while successful responses required about 52 ms. Direct assets avoid invoking application runtime code.

Verification

• pnpm install --frozen-lockfile
• pnpm docs:typecheck
• pnpm docs:lint
• pnpm docs:verify-maintenance
• pnpm docs:verify-deployment
• pnpm docs:verify-release
• PLANR_DOCS_URL=http://127.0.0.1:8788 pnpm docs:verify-release-live
• PLANR_DOCS_URL=http://127.0.0.1:8788 pnpm docs:verify-shell
• pnpm --filter @planr/docs exec alchemy plan --stage prod

Local browser proof covered 68 page states, 20 interactions, and 23 axe pages with zero serious or critical findings.