fix(ci): make pip-audit blocking — skip editable packages instead of continue-on-error

The local arkforge-trust-layer package is not on PyPI, causing pip-audit
to skip it. Using --skip-editable cleanly handles this while keeping the
step blocking for real vulnerabilities in dependencies.

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

Author: desiorac

.github/workflows/ci.yml

@@ -30,5 +30,4 @@ jobs:
       - name: Audit dependencies
         run: |
           pip install pip-audit
-          pip-audit
-        continue-on-error: true
+          pip-audit --skip-editable