Update Plotly to 3.3.1 and add heatmap click event

[nojaf]

📝 Summary

Add support for click events on plotly heatmaps and upgrade plotly.js to v3.

🔍 Description of Changes

This PR has two parts:

Step 1: Upgrade plotly.js from v2 to v3

Updated plotly.js from ^2.35.3 to ^3.3.1. This builds on top of #8238 which replaced react-plotly.js with a vendored Plot component. The v3 upgrade results in a smaller bundle (plotly chunk went from ~11 MB to ~4.8 MB) and no longer produces any buffer-related build warnings.

Step 2: Add heatmap click support

Heatmaps don't support box/lasso selection (onSelected), so clicking a cell previously did nothing. This adds:

• A plotly_click event listener in the vendored Plot component (Plot.tsx).
• An onClick handler in PlotlyPlugin.tsx, guarded to only process heatmap traces so it doesn't interfere with the existing onSelected flow for scatter/bar/line charts.
• A fallback in extractPoints that picks standard point keys (x, y, z, etc.) directly from the point data for heatmaps, instead of relying on the hovertemplate parser. The parser doesn't work for heatmaps because they either have no hovertemplate or use a format (e.g. Day: %{x}) that the parser's key=%{selector} regex doesn't match.

A heatmap section was added to the existing plotly_example.py smoke test for manual QA.

📋 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).
• Tests have been added for the changes made.
• Documentation has been updated where applicable, including docstrings for API changes.
• Pull request title is a good summary of the changes - it will be used in the release notes.

//cc @mscolnick

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Feb 10, 2026 9:26am

[ubertidavide]

Hello, I've opened an upstream PR on Plotly.js that natively solves the missing heatmap event payload issue at the core library level: #7920 - fix(heatmap): add eventData handler for proper click event data
Once merged in Plotly.js, plotly_click events will natively expose 2D matrix coordinates pointNumber: [row, col] and z values, eliminating the need for custom frontend extractPoints workarounds!