Add a Geo/map chart with Choropleth, points, pie, arc and path layers

[IPWright83]

Summary

Adds <Geo>, a map/choropleth chart family. It's a composition root like <XYChart> - self-contained, but rather than a single fixed plot it composes any combination of new layers as children, all sharing one d3-geo projection fitted to the plot area:

• <Choropleth> - shades each region of a GeoJSON/TopoJSON geography by a quantized color scale, joined against the chart's data by a region key (e.g. population by country/continent).
• <GeoPoints> - plots a marker per row at its lat/lon, optionally sized by a value and colored by category.
• <GeoPie> - plots a small Pie/Donut glyph per location, summarizing that location's rows by category (e.g. energy mix per city).
• <GeoArcs> - draws a great-circle flow line between a source/target lat/lon pair per row (e.g. migration or trade between regions).
• <GeoPaths> - connects each group's rows into a single ordered route across the map (e.g. a tracked animal's migration path).

Any combination of layers can be composed onto one <Geo> - see the Composed story/Composing layers doc section.

Supports both GeoJSON and TopoJSON (via the new topojson-client dependency) for features, any standard d3-geo projection (equalEarth/mercator/naturalEarth1/orthographic/albersUsa/albers/azimuthalEqualArea) or a custom projection factory, and Canvas rendering via useCanvas.

Implementation notes

• New renderGeoPath Canvas primitive in @chart-io/core (registered under the "geo" path type in renderElements), shared by every layer that draws an arbitrary projected shape (regions, arcs, routes). It replays the SVG d string's M/L/Z commands directly rather than depending on the Path2D global, which isn't available in every Canvas host environment (e.g. jsdom's canvas polyfill).
• New normalizeGeoFeatures core util converts either a plain GeoJSON Feature/FeatureCollection or a TopoJSON Topology into one consistent FeatureCollection.
• New <ShapesPlot> generic React primitive (alongside the existing NodesPlot/RectsPlot/LinksPlot/LabelsPlot) renders arbitrary filled/stroked shapes from a d accessor - powers <Choropleth>'s regions, <GeoArcs>'s flow lines and <GeoPaths>'s routes.
• The shared projection is threaded through a GeoContext provided by an internal GeoLayer (the real direct child of <Chart>, carrying the isPlot/requiresVirtualCanvas flags <VirtualCanvas> looks for) - not the Redux store, to keep this contained to the react package.
• New world_map_dataset.js Storybook dataset - deliberately low-resolution, hand-authored continent bounding regions (not real coastlines), so the Storybook/Chromatic build has no external basemap dependency.

Test plan

• pnpm --filter @chart-io/core test / lint / types / build
• pnpm --filter @chart-io/react test / lint / types / build
• New unit tests for every layer plus a Canvas-mode image snapshot test (packages/react/src/lib/components/Plots/Geo/Geo.unit.tsx)
• New unit tests for normalizeGeoFeatures (packages/core/src/utils/geo/normalizeGeoFeatures.unit.ts)
• Built Storybook and visually verified each new story (Choropleth, GeoPoints, GeoPie, GeoArcs, GeoPaths, composed layers) in a headless browser
• Added a changeset

🤖 Generated with Claude Code

https://claude.ai/code/session_01SHs98Edsbh6eZLEKKhJMS3

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Generated by Claude Code

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🦋 Changeset detected

Latest commit: 15c0009

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@chart-io/core	Minor
@chart-io/react	Minor

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