fix: align column headers with text_justify_columns setting

[maxkoretskyi]

Summary

Column headers now follow the same alignment as cell data when using text_justify_columns.

Closes #7967

Description of Changes

When text_justify_columns is set (e.g., {"Age": "right"}), only cell data was aligned — column headers stayed left-aligned, creating a visual mismatch.

The fix passes the justify value from generateColumns through to DataTableColumnHeader, which applies:

• flex-row-reverse for right-aligned columns (swaps the sort/filter icon to the left)
• text-right / text-center on the header text span

Before:
Headers left-aligned, data right-aligned.

After:
Headers match the cell data alignment.

Files changed:

• column-header.tsx — accepts justify prop, applies alignment classes
• columns.tsx — passes justify to the header component
• columns.test.tsx — adds test for header justification

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.

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Feb 7, 2026 4:25pm