initial: test-helper agent for e2e platform feature coverage

Two skills:
  - echo(text): trivial sub-second response. Used by approval-mode tests
    that need a fast handoff target.
  - try_scope_expansion(reason, read_patterns, ttl_seconds, mode):
    deliberately calls ctx.request_scope() with caller-supplied args so
    e2e tests can exercise the orchestrator's scope-negotiation flow
    end-to-end without inventing a real workload that happens to need
    extra files.

Standard A2A scaffold: Dockerfile FROM a2a-pack-base, /invoke/{skill} +
/.well-known/agent-card served by the SDK's serve/asgi.py adapter, deploy/
manifests for k8s, Gitea Actions workflow that builds + bumps the image
SHA.

Public, low resources (50m CPU / 128Mi mem). Not exposed via the public
ingress in any meaningful way — only the in-cluster Service is consulted
by the orchestrator's call_agent.

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

.gitea/workflows/build.yml

@@ -0,0 +1,35 @@
+name: build
+on:
+  push:
+    branches: [main]
+    paths-ignore:
+      - 'deploy/**'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: build image
+        run: |
+          IMG=registry.a2acloud.io/agents/test-helper
+          docker build -t "$IMG:$GITHUB_SHA" -t "$IMG:latest" .
+          docker push "$IMG:$GITHUB_SHA"
+          docker push "$IMG:latest"
+
+      - name: bump deploy manifest
+        run: |
+          IMG=registry.a2acloud.io/agents/test-helper
+          sed -i "s|image: $IMG:.*|image: $IMG:$GITHUB_SHA|" deploy/20-deployment.yaml
+          git config user.email "ci@a2a.local"
+          git config user.name "ci"
+          git add deploy/20-deployment.yaml
+          if git diff --staged --quiet; then
+            echo "no manifest changes"
+          else
+            git commit -m "ci: bump image to $GITHUB_SHA"
+            git push "http://gitea_admin:${{ secrets.ADMIN_PW }}@gitea-http.gitea.svc.cluster.local:3000/gitea_admin/test-helper.git" HEAD:main
+          fi