docs(cloud-run): Clarify multi-agent project structure for Cloud Run deployment

Author: triangle-z

docs/deploy/cloud-run.md

@@ -200,6 +200,23 @@ export GOOGLE_GENAI_USE_VERTEXAI=True
         CMD ["sh", "-c", "uvicorn main:app --host 0.0.0.0 --port $PORT"]
         ```
 
+    #### Defining Multiple Agents
+
+    You can define and deploy multiple agents within the same Cloud Run instance by creating separate folders in the root of `your-project-directory/`. Each folder represents one agent and must define a `root_agent` in its configuration.
+
+    Example structure:
+
+    ```txt
+    your-project-directory/
+    ├── capital_agent/
+    │   ├── __init__.py
+    │   └── agent.py       # contains `root_agent` definition
+    ├── population_agent/
+    │   ├── __init__.py
+    │   └── agent.py       # contains `root_agent` definition
+    └── ...
+    ```
+
     #### Deploy using `gcloud`
 
     Navigate to `your-project-directory` in your terminal.