Clean up dataclasses reprs

[dmontagu]

Remove defaults from the repr of all dataclasses in messages.py. This cleans up the way a lot of things print out, you can see in the updates to the docs/docstrings.

I think we could probably do this for all dataclasses in the library but don't necessarily need to let that get in the way of this improvement.

[hyperlint-ai]

PR Change Summary

Cleaned up the representation of dataclasses in the messages module by removing default values from their repr methods, enhancing the clarity of printed outputs.

• Removed default values from the repr of all dataclasses in messages.py
• Improved the readability of printed outputs in various documentation sections
• Considered extending similar changes to all dataclasses in the library

Modified Files

• docs/agents.md
• docs/api/models/function.md
• docs/direct.md
• docs/message-history.md
• docs/tools.md

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[github-actions]

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