Function buildArcPath

buildArcPath(
    samples: SunSample[],
    width: number,
    height: number,
    maxAltitude?: number,
): string
Build the SVG path data (M x y L x y …) tracing the day's altitude arc.
Parameters
- samples: SunSample[]
  The day's samples, e.g. from sampleSunDay.
- width: number
  Drawing width in SVG user units (px).
- height: number
  Drawing height in SVG user units (px).
- maxAltitude: number = 75
  Altitude in degrees that maps to the top of the box. Default 75.
Returns string
An SVG path d string, or '' when samples is empty.