Function planeAxesFor

planeAxesFor(
    n: readonly [number, number, number],
): {
    u: readonly [number, number, number];
    v: readonly [number, number, number];
}
The plane's in-plane ENU axes for a unit normal n: u is horizontal (east/north components only — the "width" axis), v = n × u completes the basis (vertical for an untilted plane — the "length" axis). Shared by the clip volume, the plane visual, and the widget's handles so they always agree.
Parameters
- n: readonly [number, number, number]
  The plane's unit ENU normal.
Returns { u: readonly [number, number, number]; v: readonly [number, number, number] }