Stabilize Pages post-deploy verification against propagation lag

[Copilot]

The Verify what is published GitHub Actions job was failing because it retried only the homepage fetch, while all other published-site checks ran once and could hit stale CDN content right after deploy. This update makes post-deploy verification resilient to Pages propagation delays without relaxing assertions.

• Verification loop now covers full validation set

  • Moved all fetches and content assertions inside a single retry loop.
  • Keeps existing checks for routes, sitemap, robots, assets, PDF signature, and 404 content.

• Retry behavior tuned for eventual consistency

  • Expanded attempts from 5 to 8 with the existing wait interval.
  • Job now succeeds only when the full check set passes in one attempt; otherwise fails with a clear terminal message.

• Failure mode remains strict

  • No assertion was removed or weakened.
  • Change targets flakiness from publish timing, not correctness criteria.

for attempt in 1 2 3 4 5 6 7 8; do
  if curl ... \
    && grep ... \
    && curl ... \
    && head -c 5 /tmp/cv.pdf | grep -q "%PDF-" \
    && curl -sS "$site/rien-ici" | grep -qi "introuvable\|404"; then
    echo "verified $site"
    exit 0
  fi
  sleep 10
done
exit 1