Refresh launch docs that still describe pre-Discussions / pre-Zendesk state

## Task

Historical launch docs still disagree with current main.

## Files

- `docs/launch/LAUNCH-CHECKLIST.md` — check off GitHub Discussions; replace stale pytest/coverage numbers with a pointer to `docs/project-metrics.md`
- `docs/launch/LAUNCH-READINESS-REVIEW.md` — v1.1 still says Zendesk not started and httpOnly cookies pending; both shipped

Keep the “historical snapshot” framing. Do not pretend old scores are current.

## Acceptance criteria

- [ ] Discussions item checked or marked shipped via #11
- [ ] Zendesk/cookie lines match `docs/ROADMAP.md` and `docs/release/known-limitations.md`
- [ ] Test counts are not invented; link project-metrics

Compare docs/launch/LAUNCH-CHECKLIST.md and docs/launch/LAUNCH-READINESS-REVIEW.md with docs/project-metrics.md, docs/ROADMAP.md, and docs/release/known-limitations.md. Check the Discussions status via #11 and verify the Zendesk and httpOnly cookie wording against those references. Done means both launch documents retain their historical-snapshot framing, link project metrics instead of inventing counts, and match the current shipped status.

Written by the indexing model from the issue text.