docs: Add complete e2e working quickstart link across all quickstart sections (#296)

Author: anubhav756

packages/toolbox-core/README.md

@@ -97,6 +97,11 @@ if __name__ == "__main__":
     asyncio.run(main())
 ```
 
+> [!TIP]
+> For a complete, end-to-end example including setting up the service and using
+> an SDK, see the full tutorial: [**Toolbox Quickstart
+> Tutorial**](https://googleapis.github.io/genai-toolbox/getting-started/local_quickstart)
+
 > [!IMPORTANT]
 > If you initialize `ToolboxClient` without providing an external session and
 > cannot use `async with`, you must explicitly close the client using `await

packages/toolbox-langchain/README.md

@@ -73,6 +73,11 @@ for s in agent.stream({"messages": [("user", prompt)]}, stream_mode="values"):
         message.pretty_print()
 ```
 
+> [!TIP]
+> For a complete, end-to-end example including setting up the service and using
+> an SDK, see the full tutorial: [**Toolbox Quickstart
+> Tutorial**](https://googleapis.github.io/genai-toolbox/getting-started/local_quickstart)
+
 ## Usage
 
 Import and initialize the toolbox client.

packages/toolbox-llamaindex/README.md

@@ -69,6 +69,11 @@ async def run_agent():
 asyncio.run(run_agent())
 ```
 
+> [!TIP]
+> For a complete, end-to-end example including setting up the service and using
+> an SDK, see the full tutorial: [**Toolbox Quickstart
+> Tutorial**](https://googleapis.github.io/genai-toolbox/getting-started/local_quickstart)
+
 ## Usage
 
 Import and initialize the toolbox client.