ci: bump standards scan-reusable pin to e9c8888 (un-staled scanner cache) (#325)

## Summary

Bumps the Hypatia scan-reusable pin in
`.github/workflows/hypatia-scan.yml`
from `d7c2271` to `e9c8888` (current standards `main`).

standards#441 (merged) source-pins the scanner build cache so the clone
+
`mix escript.build` re-run when hypatia `main` advances, instead of
restoring the first scanner ever cached forever. This bump lets fleet
scans pick up the current scanner ruleset.

The earlier `GITHUB_TOKEN not set` warnings were already resolved by the
existing `d7c2271` pin (which contains standards#429) plus `secrets:
inherit`; this is purely the cache-freshness follow-up.

**Note:** this only affects the *scan* path. Fleet actuation/dispatch
uses
`HYPATIA_DISPATCH_PAT`, a separate token, and is unaffected by this
change.

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

---
_Generated by [Claude
Code](https://claude.ai/code/session_017wGTeLwiBGJ5rETC3QT4Pm)_

Co-authored-by: Claude <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/hypatia-scan.yml

@@ -27,7 +27,7 @@ permissions:
 
 jobs:
   hypatia:
-    uses: hyperpolymath/standards/.github/workflows/hypatia-scan-reusable.yml@d7c22711e830e1f383846472f6e9b99debdb201e
+    uses: hyperpolymath/standards/.github/workflows/hypatia-scan-reusable.yml@e9c8888769a703924cc3c0d717900960d78aea00
     secrets: inherit
     # Total caller-side wall-clock cap for the reusable. Matches
     # Hypatia's `missing_timeout_minutes` rule expectation. The scan is