/**
 * Compute the radius-ratio shape quality of a tetrahedron given by 4 vertex
 * indices into the points array. Normalised so a regular tet returns 1 and
 * a degenerate (zero-volume) tet returns 0.
 *
 * Formula: 3 · r_in / r_circ where
 *   r_in  = inscribed-sphere radius = 3·|V| / S_total
 *   r_circ = circumscribed-sphere radius
 *   S_total = sum of the 4 face areas
 *   |V| = absolute signed volume
 *
 * Quality bands (rough rule of thumb for the radius-ratio metric):
 *   1.0       regular tet
 *   ≥ 0.5     well-shaped, safe for FEM / fluid
 *   0.1–0.5   acceptable, may slow convergence
 *   0.01–0.1  sliver — usually a target for flipping / smoothing
 *   < 0.01    near-degenerate, almost flat
 *
 * Indexed form (not mesh-bound) so callers can score hypothetical tets
 * during a flip-candidate search without committing the flip first. The
 * existing mesh-form wrapper {@link compute_tetrahedron_quality} fetches
 * the four vertex IDs and forwards here.
 *
 * @param {ArrayLike<number>} points flat (x,y,z) positions
 * @param {number} a vertex index
 * @param {number} b vertex index
 * @param {number} c vertex index
 * @param {number} d vertex index
 * @returns {number} quality in [0, 1]
 */
export function tetrahedron_compute_quality(points: ArrayLike<number>, a: number, b: number, c: number, d: number): number;
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