fix(runtime): fail closed without bubblewrap; install it in CI and the image

The function runtime silently ran untrusted code as a plain process when
/usr/bin/bwrap was missing. The CI job image (node:24-bookworm) has no
bubblewrap, so the stage-6 sandbox tests got 'leak' no matter which
capabilities the runner granted. Now execute() returns an error outcome
instead, CI installs bubblewrap, and the runtime image ships it
(bubblewrap: required by the sandbox, from Debian).

Also commits the runner's job-container options (SYS_ADMIN + AppArmor
unconfined), already live on VM103, needed for bwrap to create namespaces.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -21,6 +21,8 @@ jobs:
       - uses: actions/checkout@v4
         with:
           github-server-url: ${{ env.GITEA_INTERNAL_URL }}
+      # The function-runtime sandbox tests need bubblewrap; the runtime refuses to run functions without it.
+      - run: apt-get update -qq && apt-get install -y -qq --no-install-recommends bubblewrap >/dev/null && bwrap --version
       - run: npm ci
       - run: npm run check