ci: repin orphan reusable SHAs (97df7621/4fdf4314 → live) (#33)

## Summary

The workflow(s) in this repo pinned `hyperpolymath/standards` reusable
workflow(s) at orphan SHAs — commits no longer reachable from
`standards/main`.

## Fix

Re-pin to the reachable merge-commit SHAs:
- `hypatia-scan-reusable.yml@97df7621` →
`@915139d73560e65a8240b8fc7768698658502c89`
- `rust-ci-reusable.yml@4fdf4314` →
`@cc5a372af1af1b202c17f1b21efd954e6c038bef`

## Reference

- Audit:
hyperpolymath/standards/docs/audits/audit-hypatia-pin-orphan-2026-05-27.adoc
- Detector: hypatia rule WF016 in hyperpolymath/hypatia#393

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/hypatia-scan.yml

@@ -25,5 +25,5 @@ permissions:
 
 jobs:
   hypatia:
-    uses: hyperpolymath/standards/.github/workflows/hypatia-scan-reusable.yml@97df762107501909f50bb770e9bc200b6c415600
+    uses: hyperpolymath/standards/.github/workflows/hypatia-scan-reusable.yml@915139d73560e65a8240b8fc7768698658502c89
     secrets: inherit