Enhancement [DEV-12685] Add colors to chart tooltips

[jayb]

Summary

This adds colored shapes to chart tooltip indicating which series the items in the tooltip belong to.

• If there is only one series, or the legend is hidden, it does not show colors
• If more than one series resolves to the same color, it does not show colors
• It does not show colors for gradient legends
• If the legend uses boxes, it shows boxes

Testing Steps

Look at as many charts as possible and see if the colors shown in tooltips make sense.

[Copilot]

Pull request overview

Adds optional, legend-consistent color/shape markers to chart tooltips so users can visually map tooltip rows back to series.

Changes:

• Introduces a typed tooltip-row model (with optional marker metadata) and marker-eligibility logic in a shared helper.
• Updates core tooltip rendering (LinearChart/PieChart via useTooltip, plus Bar/Scatter HTML-tooltips) to render aligned marker swatches when appropriate.
• Adds supporting tooltip marker styles plus Storybook smoke stories/tests to exercise marker/no-marker scenarios (including small multiples).

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
packages/core/components/ui/tooltip.scss	Adds layout + swatch styles for tooltip marker column.
packages/chart/src/types/ChartConfig.ts	Extends legend config with tooltipLegendVisible? to preserve “source legend visible” semantics for small multiples.
packages/chart/src/hooks/useTooltip.tsx	Converts tooltip payload to typed rows and renders optional marker column in React tooltip list items.
packages/chart/src/helpers/tooltipHelpers.ts	Adds shared marker eligibility/color resolution + HTML tooltip builders for series tooltips.
packages/chart/src/helpers/tests/tooltipHelpers.test.ts	Adds Vitest coverage for marker eligibility, uniqueness suppression, and HTML rendering.
packages/chart/src/components/SmallMultiples/SmallMultipleTile.tsx	Propagates “source legend visible” state into hidden tile legends to enable markers when appropriate.
packages/chart/src/components/ScatterPlot/ScatterPlot.jsx	Switches tooltip HTML generation to shared builder that can include markers.
packages/chart/src/components/PieChart/PieChart.tsx	Adapts tooltip data handling to new row-array format and passes marker-column flag to row renderer.
packages/chart/src/components/LinearChart.tsx	Adapts tooltip data handling to new row-array format and passes marker-column flag to row renderer.
packages/chart/src/components/BarChart/components/BarChart.Vertical.tsx	Uses shared HTML tooltip builder for consistent markup + optional markers.
packages/chart/src/components/BarChart/components/BarChart.StackedVertical.tsx	Uses shared HTML tooltip builder for consistent markup + optional markers.
packages/chart/src/components/BarChart/components/BarChart.StackedHorizontal.tsx	Uses shared HTML tooltip builder for consistent markup + optional markers.
packages/chart/src/components/BarChart/components/BarChart.Horizontal.tsx	Uses shared HTML tooltip builder for consistent markup + optional markers.
packages/chart/src/_stories/Chart.tooltip.smoke.stories.tsx	Adds stories covering marker rendering and “no markers” cases (legend hidden/gradient/patterns).
packages/chart/src/_stories/Chart.SmallMultiples.smoke.stories.tsx	Adds assertions around presence/absence of marker markup in small-multiple tooltip HTML.

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