[docs] Add Google-style docstrings for dspy/adapters/types/audio.py Audio class

[mediix]

What feature would you like to see?

I would like to improve docstring coverage for the Audio class and related functions in dspy/adapters/types/audio.py. This includes:

• Audio class docstring
• format() method
• from_url() method (expand from one-liner)
• from_file() method (expand from one-liner)
• from_array() method (expand from one-liner)
• encode_audio() function (expand from one-liner)

Ref: #8926

Would you like to contribute?

• Yes, I'd like to help implement this.
• No, I just want to request it.

Additional Context

The Audio class currently has no class-level docstring and only minimal one-liner descriptions for methods. I will add comprehensive Google-style docstrings with proper Args, Returns, Raises, and Example sections following the pattern in dspy/adapters/types/history.py.

[chenmoneygithub]

@mediix Thank you! Looking forward to your PR!