fix(sandbox):deer-flow-provisioner container fails to start in local execution mode (#889)

CONTRIBUTING.md

@@ -41,6 +41,8 @@ Docker provides a consistent, isolated environment with all dependencies pre-con
    ```bash
    make docker-start
    ```
+   `make docker-start` reads `config.yaml` and starts `provisioner` only for provisioner/Kubernetes sandbox mode.
+
    All services will start with hot-reload enabled:
    - Frontend changes are automatically reloaded
    - Backend changes trigger automatic restart
@@ -56,7 +58,7 @@ Docker provides a consistent, isolated environment with all dependencies pre-con
 ```bash
 # Build the custom k3s image (with pre-cached sandbox image)
 make docker-init
-# Start all services in Docker (localhost:2026)
+# Start Docker services (mode-aware, localhost:2026)
 make docker-start
 # Stop Docker development services
 make docker-stop
@@ -77,7 +79,8 @@ Docker Compose (deer-flow-dev)
   ├→ nginx (port 2026) ← Reverse proxy
   ├→ web (port 3000) ← Frontend with hot-reload
   ├→ api (port 8001) ← Gateway API with hot-reload
-  └→ langgraph (port 2024) ← LangGraph server with hot-reload
+   ├→ langgraph (port 2024) ← LangGraph server with hot-reload
+   └→ provisioner (optional, port 8002) ← Started only in provisioner/K8s sandbox mode
 ```
 
 **Benefits of Docker Development**:
@@ -238,6 +241,13 @@ cd frontend
 pnpm test
 ```
 
+### PR Regression Checks
+
+Every pull request runs the backend regression workflow at [.github/workflows/backend-unit-tests.yml](.github/workflows/backend-unit-tests.yml), including:
+
+- `tests/test_provisioner_kubeconfig.py`
+- `tests/test_docker_sandbox_mode_detection.py`
+
 ## Code Style
 
 - **Backend (Python)**: We use `ruff` for linting and formatting