fix(ci): wrap hashFiles in expression syntax in secret-scanner

Job-level `if:` with bare `hashFiles()` causes a workflow file
parse error. Wrapping in `${{ }}` fixes the expression evaluation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/secret-scanner.yml

@@ -37,7 +37,7 @@ jobs:
   # Rust-specific: Check for hardcoded crypto values
   rust-secrets:
     runs-on: ubuntu-latest
-    if: hashFiles('**/Cargo.toml') != ''
+    if: ${{ hashFiles('**/Cargo.toml') != '' }}
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v4