Status pages: withErrorPage 503→500 regression and RFC-0043 deviations (follow-up to #162) #167

Follow-ups to RFC-0043 PR 1 (#162) from the adversarial review; none is in a release yet (status pages ship with 0.6.4). Fold them into RFC-0043 PR 2 or a small fix(astro-renderer) PR before the next tag.

Medium

1. withErrorPage turns the starter's own not-published 503 into a 500 error page with a false error log (packages/astro-renderer/src/cloudflare-entry.ts:181-183): the 5xx→error rewrite catches every 5xx the theme returns, including the 503 the starter sends for an unpublished site when the request reaches Astro. Only rewrite thrown errors / 500s, or let a response marked by the renderer (x-cloudhal-status) through.

Low (RFC-0043 deviations)

2. A store read failure before rendering answers 500 error without Retry-After, not 503 unavailable with Retry-After: 300, while /__cloudhal/health treats the same failure as 503 (runtime-workerd.ts:189-190).
3. The error page is always English and never shows the site name, even when the site is already loaded (cloudflare-entry.ts:175); use the site's locale and name when they are known.
4. An invalid preview token on a feed, sitemap or JSON path still serves the published content (cloudflare-entry.ts:665), and the preview-link failure reason is still echoed on machine and media paths (runtime-workerd.ts:341), contrary to Decision 12.
5. docs/adr/0012-cloudflare-deployment.md:15 still says invalid preview tokens fall back to the published page.
6. Translation docs: the status catalog (packages/astro-renderer/src/status-strings/) is missing from .agents/skills/translate/SKILL.md:16, DESIGN.md §1, the Weblate guide and ADR-0034, which still describe the exchange as Studio-only.
7. RFC-0043 §1.9: say that health answers a short-cached 404 on a host that maps to no site (RFC-0034 §4), not {ok,state}.

Done when

• 1–4 have unit cases in packages/astro-renderer/test (the 503 path through withErrorPage, the store failure, the locale/site name, the machine-path token).
• 5–7 docs updated. pnpm check green.

Source: adversarial review run after the 0.6.3 release (178 agents, 47 confirmed findings).