fix(types): parameterize RadarController with its 'radar' chart type

[marina-semeia]

RadarController is declared as the unparameterized DatasetController, so its TType falls back to the generic ChartType:

export type RadarController = DatasetController

As a result, a subclass of RadarController loses radar-specific typing. For example, getParsed() returns the union of all parsed data types instead of RadialParsedData:

class CustomRadarController extends RadarController {
  override updateElements(points, start, count, mode) {
    for (let i = start; i < start + count; i++) {
      const r = this.getParsed(i).r;
      // TS error: Property 'r' does not exist on type
      // 'number | CartesianParsedData | BarParsedData | BubbleParsedData | RadialParsedData'.
    }
  }
}

This is a common need when extending the radar controller (e.g. to position points between grid lines instead of on them).

Changes

• RadarController is now DatasetController<'radar'> in src/types/index.d.ts.
• Added a type test in test/types/controllers/radar_controller_subclass.ts (fails with TS2339 without the fix, passes with it).

Note

The other built-in controllers (BarController, LineController, BubbleController, DoughnutController, …) are declared the same unparameterized way. I kept this PR scoped to RadarController, but I'm happy to extend it to the others if you'd prefer a consistent change.