ci(secret-scan): rename caller job key secret-scan -> scan (D243) (#37)

## What

Rename the secret-scanner caller job key `secret-scan` → `scan` in
`.github/workflows/secret-scanner.yml`, so the check context becomes
`scan / gitleaks` — the context the estate Secret-Scan-Floor ruleset
(D243/D244) requires. One-line change; reusable pin, triggers and
permissions unchanged. actionlint output is identical before and after.

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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/secret-scanner.yml

@@ -18,7 +18,7 @@ permissions:
   actions: read
   contents: read
 jobs:
-  secret-scan:
+  scan:
     uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@bd0df9ead7faf0cdfe0e13e7966d91e28d0101d4
     secrets: inherit
     permissions: