FR : Programmatically Collapse a Step (`step.close()` or `step.status = "finished"`)

[dominpm]

trafficstars

Summary
It would be incredibly useful to have a way to programmatically collapse a step in the Chainlit UI once it's complete — especially after tools or long-running processes finish streaming.

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Why This Matters

• Long tool steps (e.g., scraping, web search) stream lots of tokens.
• After they complete, we want to visually signal completion and reduce clutter.
• Currently, there is no way to collapse or mark a step as "done" via code.

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