[UNIT] Final review of Unit 2.1 on smolagents - release 25/2/25

[burtenshaw]

This PR is to review the final changes for the unit on the smolagents library.

Prose to review @pcuenca @simoninithomas @davidberenstein1957

• units/en/unit2/smolagents/code_agents.md
• units/en/unit2/smolagents/introduction.md
• units/en/unit2/smolagents/multi_agent_systems.md
• units/en/unit2/smolagents/retrieval_agents.md
• units/en/unit2/smolagents/tool_calling_agents.md
• units/en/unit2/smolagents/tools.md
• units/en/unit2/smolagents/why_use_smolagents.md

Outstanding work for other PRs

• @sergiopaniego combine vision and browser agents, and mention best open model
• @simoninithomas @sergiopaniego add banner image to introduction [UNIT] smolagents framework - release 24/2/25 #102 (comment)
• @burtenshaw add page on quiz

[simoninithomas]

First of all congratulations on making this huge unit 2.1 @sergiopaniego. The content is simply excellent.
Most of my review was not on the content directly but on avoiding big block of text by adding bold and spaces.

But I kept your writing style, even if it’s different from unit 1, your style is excellent. It’s super smooth, easy to read, super well explained, focused on the student so yeah simply excellent (where have you been when I was writing deep rl course 🤣).

Feel free to refuse the suggestions you think are not relevant.

I have some changes asked though:

1. I saw you put notebooks, I didn’t reviewed them yet (I’m doing this afternoon but I think we should add the links in the sections. An open with colab link.
2. I'm creating a short conclusion. Feel free to change the content.