fix: reject warp configs with non-positive-integer degree

src/config.test.ts

@@ -58,4 +58,14 @@ describe('loadConfig', () => {
     const cfg = await loadConfig('config.json');
     expect(cfg.calibration).toBeNull();
   });
+
+  it('rejects a warp with a non-positive-integer degree', async () => {
+    const square = [[0, 0], [10, 0], [10, 10], [0, 10]] as [number, number][];
+    // A negative degree makes termCount collapse to 0, so empty coeff arrays would
+    // vacuously validate — guard against that.
+    const warp = { degree: -1, fwd: { norm: { off: [0, 0], scl: [1, 1] }, cu: [], cv: [] }, inv: { norm: { off: [0, 0], scl: [1, 1] }, cu: [], cv: [] } };
+    mockFetch({ streamUrl: 'x', calibration: { imagePoints: square, machinePoints: square, warp } });
+    const cfg = await loadConfig('config.json');
+    expect(cfg.calibration).toBeNull();
+  });
 });

src/config.ts

@@ -35,7 +35,9 @@ function parsePolyMap(m: unknown, degree: number): PolyMap | null {
 function parseWarp(w: unknown): PolyWarp | null {
   if (!w || typeof w !== 'object') return null;
   const o = w as Record<string, unknown>;
-  if (!isFiniteNumber(o.degree)) return null;
+  // Require a positive integer degree: a negative/zero/fractional degree makes termCount
+  // collapse to 0, which would vacuously accept empty coefficient arrays (a garbage warp).
+  if (!isFiniteNumber(o.degree) || !Number.isInteger(o.degree) || o.degree < 1) return null;
   const fwd = parsePolyMap(o.fwd, o.degree);
   const inv = parsePolyMap(o.inv, o.degree);
   if (!fwd || !inv) return null;