fix(highlighter): Fix sorting logic for highlighted geometries

[andrimal]

Summary

The highlighter now respects the series sorting order.

Details

When 2 or more point geometries overlap at the same position (x, y, radius):

• Highlighted points: They are pre-sorted by sortOrder so the topmost point renders last and its color appears on top
• Hovered geometries: They are now deduplicated to keep only the topmost point (highest sortOrder), preventing semi-transparent highlight colors from mixing

Screenshots

Multiple overlapping points:

Before:

After:

Issues

fix #1921 and fix #2752

Checklist

• The proper chart type label has been added (e.g. :xy, :partition)
• The proper feature labels have been added (e.g. :interactions, :axis)
• All related issues have been linked (i.e. closes #123, fixes #123)
• The proper documentation and/or storybook story has been added or updated
• The code has been checked for cross-browser compatibility (Chrome, Firefox, Safari, Edge)
• Visual changes have been tested with light and dark themes

[andrimal]

buildkite update vrt

[andrimal]

buildkite update vrt

[andrimal]

buildkite test this

[mariairiartef]

LGTM