fix(ci): hypatia-scan workdir (${{ env.HOME }} resolves empty)

The Build step set working-directory: ${{ env.HOME }}/hypatia, but
env.HOME is not a workflow env var, so it resolved to /hypatia and the
job failed with 'No such file or directory'. GitHub-hosted ubuntu
runners always have HOME=/home/runner; pin the path accordingly.

Unblocks the 'Hypatia Neurosymbolic Analysis' check estate-wide.

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

Author: tanush5800

.github/workflows/hypatia-scan.yml

@@ -37,7 +37,7 @@ jobs:
           fi
 
       - name: Build Hypatia scanner (if needed)
-        working-directory: ${{ env.HOME }}/hypatia
+        working-directory: /home/runner/hypatia
         run: |
           if [ ! -f hypatia-v2 ]; then
             echo "Building hypatia-v2 scanner..."