docs: add react agent guide using functional API

[ccurme]

No description provided.

[nfcampos]

• should we make each tool a @task?
• I'd probably suggest using concurrent.futures.as_completed when waiting for the results of the tool calls, but not necessary

[vbarda]

why @tool(response_format="content_and_artifact")?

[ccurme]

this isn't needed, will remove

[ccurme]

• should we make each tool a @task?

@nfcampos is there a good way to associate the name of a tool (e.g., from a tool call) to a task?

One option is something like

def _make_task_from_tool(tool):

    @task
    def tool_task(tool_call):
        observation = tool.invoke(tool_call)
        return ToolMessage(content=observation, tool_call_id=tool_call["id"])

    tool_task.__wrapped__.__name__ = tool.name
    return tool_task