Add Astro slot-name escaping references

[cookesan]

Adds Astro slot-name escaping references to GHSA-8hv8-536x-4wqp.

Audit refresh, July 8, 2026:

• Confirmed the live PR is open, ready for review, merge-clean, and the visible advisory check is green.
• Rechecked the merge-base diff: exactly one advisory JSON file changes (advisories/github-reviewed/2026/06/GHSA-8hv8-536x-4wqp/GHSA-8hv8-536x-4wqp.json), JSON parses, git diff --check passes, and the exact-head worktree is clean.
• Revalidated the added public references and package-version evidence in the diff; all resolve through their source site or registry.

[cookesan]

Review note: this expands GHSA-8hv8-536x-4wqp with the merged Astro slot-name escaping PR, its merge commit, the astro@6.3.3 release, and matching npm package evidence. I checked the PR head JSON against the OSV schema, confirmed withastro/astro#16737 is merged at bd84f33d68cfa7d077e0a638970e28b0a9bd83db, confirmed the release URL resolves, and confirmed npm has astro@6.3.3; the affected npm range, CVSS score, alias, and package metadata stay unchanged.