Bug in pure mcp example (missing tool name)

### What happened?

https://github.com/a2aproject/a2a-samples/blob/f140c6d5bc90297f448fdf73ab4b32c16f7cf60c/samples/python/agents/a2a-mcp-without-framework/src/no_llm_framework/server/agent.py#L153

but in jinja

https://github.com/a2aproject/a2a-samples/blob/f140c6d5bc90297f448fdf73ab4b32c16f7cf60c/samples/python/agents/a2a-mcp-without-framework/src/no_llm_framework/server/called_tools_history.jinja#L2

In jinja, should use "tool.tool" instead to avoid missing tool name in history? (or agent.py should use "name" as key?)

### Relevant log output

```shell
After writting the rendered template, currently the prompt looks like the following

...
Previous tools have been called.
- Tool:
- Arguments: {...
```

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

The issue points to two files: agent.py line 153 and called_tools_history.jinja line 2. Compare the data structure passed from agent.py (likely a dictionary with a 'tool' key) with the variable accessed in the Jinja template (currently 'tool.name'). Determine whether to change the key in the Python data or the variable in the template to make the tool name appear. Run the example to see the missing tool name in the prompt output.

Escrita pelo modelo de indexação a partir do texto da issue.