fix(worker): serve API same-origin via Cloudflare Pages Functions (GOAP-252)

[d-o-hub]

What & why

The frontend build runs on Cloudflare Pages directly (Pages Git integration, root wrangler.toml). So instead of deploying the Worker separately (which needs Cloudflare credentials, a separate origin, CORS, and VITE_API_BASE_URL), the API now rides the same Pages deployment via a Pages Function — same origin, zero credentials, no frontend change needed (the web app's production default already targets same-origin /api/*).

This is ADR-252's "preferred long-term" option, now realized.

1. functions/api/[[path]].ts (new)

A Pages Function catch-all that re-serves the existing Worker's Hono app for all /api/* requests:

export function onRequest(context) {
  return app.fetch(context.request, context.env, context.ctx);
}

Only /api/* matches — every other path falls through to the static SPA untouched.

Verified locally:

• wrangler pages functions build compiles it into a ~2MB bundle (full Hono app)
• wrangler pages dev apps/web/dist → GET /api/health returns {"ok":true} JSON 200, / still serves the SPA, and POST /api/access/request returns a proper JSON error envelope (not the HTML fallback that caused "Invalid server response")

2. release.yml — no standalone Worker deploy, no credentials

PR #1018 had restored a wrangler deploy step + workers.dev health check. With the Pages Functions model that's wrong (needs CLOUDFLARE_API_TOKEN, checks the wrong URL). Removed the deploy/secrets steps; the post-deploy health check now asserts https://do-epub-studio.pages.dev/api/health returns 200 + {"ok":true} (fail-closed, ADR-187).

3. Docs + plans

• docs/runbooks/infrastructure-setup.md rewritten for the Pages Functions model: dashboard bindings (D1 DB, R2 BOOKS_BUCKET, KV CACHE_KV) + vars, no VITE_API_BASE_URL, no wrangler deploy.
• GOAP-252 + ADR-252 updated to record the same-origin decision.
• LEARNINGS captured.

Notes on Pages constraints (all degrade gracefully, login unaffected)

• Durable Object (RATE_LIMITER) can't be created inside a Pages project → rate limiting fails open (documented rate-limit-client.ts behavior).
• Email Sending isn't a Pages Function binding → recovery email falls back to logging.

Remaining (operator, dashboard-only, no code)

Create D1/R2/KV, apply migrations, bind DB/BOOKS_BUCKET/CACHE_KV + vars (APP_BASE_URL, ENVIRONMENT, WEBAUTHN_*, signing secrets) on the Pages project, seed data, push → Pages builds frontend + functions → login works.

Verification

• Full quality gate (QUALITY_GATE_NO_SMOKE=1) passes
• ./scripts/validate-workflows.sh — all 11 workflows pass
• node scripts/check-adr-index.mjs passes
• wrangler pages functions build + wrangler pages dev verified locally

[repowise-bot]

✅ Health of changed files: 10.0
_{🚨 Change risk: high, riskier than 77% of this repo's commits.}

✅ Health gate: passed

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[cloudflare-workers-and-pages]

Deploying do-epub-studio with    Cloudflare Pages

Latest commit:	520674d
Status:	✅  Deploy successful!
Preview URL:	https://c72a9935.do-epub-studio.pages.dev
Branch Preview URL:	https://fix-pages-functions-api.do-epub-studio.pages.dev

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