fix(ci): hypatia-scan working-directory uses shell $HOME not env.HOME

${{ env.HOME }} is not set in GitHub Actions context, causing
working-directory to resolve to /hypatia instead of /home/runner/hypatia.
Use cd "$HOME/hypatia" in the run block instead.

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

Author: hyperpolymath

.github/workflows/hypatia-scan.yml

@@ -37,8 +37,8 @@ jobs:
           fi
 
       - name: Build Hypatia scanner (if needed)
-        working-directory: ${{ env.HOME }}/hypatia
         run: |
+          cd "$HOME/hypatia"
           if [ ! -f hypatia-v2 ]; then
             echo "Building hypatia-v2 scanner..."
             cd scanner