Do not record tool call id if no tool has been called

[sysradium]

I came across this issue here: #570

The problem is that if you have callbacks which modify observations like it is done here https://github.com/huggingface/smolagents/blob/main/src/smolagents/vision_web_browser.py#L66

It may happen that there is no tool call recorded yet and hence self.tool_calls is None. (ref https://github.com/sysradium/smolagents/blob/web-tool-call-issue/src/smolagents/agents.py#L871)

For example in my case it happened with vision_web_browser.py when the model did not return any Python code on the first call to it. That led to the exception here https://github.com/sysradium/smolagents/blob/web-tool-call-issue/src/smolagents/agents.py#L867 which happens right before we set memory.step.tools_calls.

So essentially you end up having data:, as an observation but no recorded tool call.

Maybe not the best solution, but I decided to just not print Call id: ... if there has been no successful tool call.

[sysradium]

@aymeric-roucher another one here if you have some time.

[aymeric-roucher]

Thank you @sysradium! Could you please add a regression test for this?

[sysradium]

@aymeric-roucher sure, will try to figure out a way.

[sysradium]

@aymeric-roucher

Added a test fixing some things along the way:

1. Added mlx into dev deps. Otherwise after running pip install -e ".[dev]" on a clean setup would get:

FAILED tests/test_models.py::ModelTests::test_get_mlx_message_no_tool - ModuleNotFoundError: Please install 'mlx-lm' extra to use 'MLXModel': `pip install 'smolagents[mlx-lm]'`

2. Modified Makefile target so that you could overrde python command. For example if you use uv now you can do:

PYTHON='uv run python' make test 
PYTHON='uv run python' make quality 

Or override it with python path you need. Just a bit of flexibility. It is backwards compatible, so if you don't override PYTHON variable you get the same behaviour.

3. With a test fixture forced MultiAgentsTests to dump data into a tmpdir, otherwise you are getting unwanted guests:

>>> gst
Untracked files:
  (use "git add <file>..." to include in what will be committed)
        agent_export/

4. Some minor type hint fixes.