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>

deploy/20-deployment.yaml

@@ -0,0 +1,70 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: test-helper
+  namespace: agents
+  labels:
+    app: test-helper
+    a2a/managed-by: control-plane
+spec:
+  replicas: 1
+  strategy:
+    type: Recreate
+  selector:
+    matchLabels:
+      app: test-helper
+  template:
+    metadata:
+      labels:
+        app: test-helper
+    spec:
+      containers:
+        - name: agent
+          image: registry.a2acloud.io/agents/test-helper:placeholder
+          imagePullPolicy: Always
+          ports:
+            - containerPort: 8000
+              name: http
+          readinessProbe:
+            httpGet: {path: /healthz, port: 8000}
+            initialDelaySeconds: 2
+            periodSeconds: 5
+          livenessProbe:
+            httpGet: {path: /healthz, port: 8000}
+            initialDelaySeconds: 10
+            periodSeconds: 15
+          resources:
+            requests: {cpu: 50m, memory: 128Mi}
+            limits: {cpu: 200m, memory: 256Mi}
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: test-helper
+  namespace: agents
+spec:
+  type: ClusterIP
+  selector:
+    app: test-helper
+  ports:
+    - name: http
+      port: 80
+      targetPort: 8000
+---
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: test-helper
+  namespace: agents
+spec:
+  rules:
+    - host: test-helper.88-99-219-120.nip.io
+      http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: test-helper
+                port:
+                  number: 80