Add PDM installer path traversal fix reference

[cookesan]

Adds PDM installer path traversal fix reference to GHSA-78v8-vpjp-cjqh.

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-78v8-vpjp-cjqh/GHSA-78v8-vpjp-cjqh.json), JSON parses, git diff --check passes, and the exact-head worktree is clean.
• Revalidated the added public references in the diff; all resolve through their source site or registry.

[cookesan]

Rechecked this reference-only PR while keeping the open Advisory Database queue current.

• The patch only adds the PDM installer path traversal fix commit reference; it does not change affected ranges, package metadata, or severity.
• The commit resolves to 41aa5f94a30e51b1a460af27312dd9dc532aad5a.
• The head advisory JSON validates against the OSV schema.

No other advisory fields are changed.