feat: Add "download" option to mo.ui.dataframe

[AnirudhDagar]

📝 Summary

Fixes #5923. This PR adds a "Download" button to mo.ui.dataframe, allowing users to export data as CSV, JSON, or Parquet. It also introduces a show_download parameter to control its visibility.

📋 Checklist

• I have read the contributor guidelines.
• For large changes, or changes that affect the public API: this change was discussed or approved through an issue, on Discord, or the community discussions (Please provide a link if applicable).
• I have added tests for the changes made.
• I have run the code and verified that it works as expected.

Disclosure: I used claude to help writing the tests.

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Project	Deployment	Preview	Comments	Updated (UTC)
marimo-docs	Ready	Preview	Comment	Sep 23, 2025 4:42pm

[mscolnick]

awesome, thank you for the contribution!

[mscolnick]

(CI is breaking for another reason, which i am fixing, so will force merge this)

[AnirudhDagar]

Thanks @mscolnick for the quick review and approval. Appreciate the pace at which marimo is being developed and improved! While working on this issue i realised search is also missing from ui.dataframe but is available in a df rendered normally. Do you think adding the search functionality to ui.dataframe is also useful? I myself use it a lot.

[mscolnick]

we can add the search as well. im not sure if there was a strong reason to not add it, i think at some point it did conflict with the filtering logic making it difficult to add, but that may have changed.

if you want to do some investigation first to see if it is possible, we are open to adding it

[AnirudhDagar]

Sounds good, let me dive deeper and get back to you if it is now possible to add it.