Add donut clusters and native Mapbox raster PMTiles

[walkerke]

Add donut charts for native GeoJSON and precomputed vector-tile clusters, and restore raster PMTiles loading on current Mapbox GL JS through its native source support. This consolidates the four existing local main commits (raster PMTiles, regenerated docs, Mapbox GL JS 3.31.0, and donut clusters) with the Census/India map follow-ups.

• Donuts show category proportions, including grouped categories and weighted totals. Cluster rendering supports compare views, and cluster paint options reach Shiny proxies.
• Count labels abbreviate millions and billions; the India total of 1,470,295,708 reads 1.5B. Donut numbers share their icons' collision rules so visible donuts retain their counts.
• Interactive legend toggles and resets preserve hexagon/custom SVG patch paint.
• Mapbox raster PMTiles use native raster sources; the obsolete custom plugin is removed. Documentation and NEWS cover the combined changes.

Validation: the focused cluster-donut and legend-patch-toggle test files pass, including native/precomputed label placement, proxy serialization, million/billion rounding boundaries, and SVG/CSS patch preservation. The India preview previously displayed 1.5B. GitHub's save-map workflow supplies separate cross-platform checks; the full package/browser suite was not rerun for these small follow-ups.