feat: add horizontal scroll option for chart legend

[jsilll]

Adds an enableHorizontalScroll option to LegendOptions that allows legend containers to scroll horizontally instead of truncating long text with ellipsis.

Changes:

• Added enableHorizontalScroll prop threaded through CoreChartProps.LegendOptions → CoreLegend → ChartLegend
• Applied overflow-x: auto on the legend list and overflow: visible on item labels when enabled

Testing

[jperals]

There are issues with the tooltip:

• It is misplaced when the labels are very long
• Very long labels are cut off
• It moves along when horizontally scrolling

scrollable-legend-horizontal-02-trimmed.mov

[jsilll]

I'll create a PR in the components repository to allow locking the horizontal position of the tooltip.

[jperals]

Would it also be an option to prevent the tooltip trigger from scrolling by having the overflowing element be a descendant of the trigger instead?

[jsilll]

I'll try that

[jperals]

Note that you'll have to update the Documenter snapshots.

You can do it by running

npx vitest run --config vite.config.unit.mjs -u src/__tests__/documenter.test.ts

[jperals]

Note: the series name in the chart popover is still a problem (it gets truncated, without even a visual indicator of the ellipsis), but this will have to be handled separately as the popover does not live in this package.

[jperals]

It would be useful to have actually really long series names in this dev page in order to test this. There could be an option for it, or alternative change the series names when legendHorizontalScroll is true.