chore: import upstream snapshot with attribution

tests/remote/triggers/README.md

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+# Remote Integration Tests for `/apps/{app_name}/trigger/*` Endpoints
+
+End-to-end tests that verify Pub/Sub push, and
+Eventarc triggers against a real ADK agent deployed to Cloud Run.
+
+## Workflow
+
+This workflow is split into three independent phases.
+
+### Phase 1: Deploy Agent
+
+Build the ADK package and deploy the echo agent to Cloud Run. This ensures that
+the service and its identity exist before any infrastructure wiring occurs.
+
+```bash
+export GCP_PROJECT_ID=your-project-id
+export SUFFIX=ea786 # Pick a unique suffix
+export SERVICE_NAME=adk-trigger-test-$SUFFIX
+
+# 1. Build local ADK wheel
+uv build --wheel --out-dir tests/remote/triggers/test_agent/wheels/
+
+# 2. Deploy Agent
+gcloud run deploy $SERVICE_NAME \
+  --source=tests/remote/triggers/test_agent \
+  --project="$GCP_PROJECT_ID" \
+  --region="us-central1" \
+  --port=8080 \
+  --quiet
+```
+
+### Phase 2: Wire Infrastructure (Terraform)
+
+Run Terraform to create the supporting infrastructure (IAM roles, Pub/Sub
+topics).
+
+```bash
+cd tests/remote/triggers/terraform
+terraform init
+terraform apply \
+  -var=project_id=$GCP_PROJECT_ID \
+  -var=service_name=$SERVICE_NAME \
+  -var=suffix=$SUFFIX
+```
+
+### Phase 3: Run Tests (Pytest)
+
+```bash
+# Run Tests from the project root
+export GCP_PROJECT_ID=your-project-id
+export SUFFIX=ea786
+pytest tests/remote/triggers/ -v -s
+```
+
+## Cleanup
+
+```bash
+# 1. Destroy infrastructure
+cd tests/remote/triggers/terraform
+terraform destroy \
+  -var=project_id=$GCP_PROJECT_ID \
+  -var=service_name=$SERVICE_NAME \
+  -var=suffix=$SUFFIX
+
+# 2. Delete Cloud Run service
+gcloud run services delete $SERVICE_NAME --project=$GCP_PROJECT_ID --region=us-central1 --quiet
+```