test: Stop asserting exact equality on sqrt results

sqrtAB compared Math.sqrt(a*b) against whole numbers with deepEqual, so
it failed on headless-gl with 7.000000476837158 for sqrt(49.0).

That value is 1 ULP above 7.0, and GLSL ES allows sqrt up to 2 ULP of
error — it is not in the correctly-rounded set with + - * /. So the
driver is conforming and the assertion was asking for a guarantee
gpu.js cannot make. Confirmed the arithmetic itself is fine: a*b returns
exactly 49, and sqrt of a literal 49 folds to exactly 7; only the
runtime sqrt carries the ULP.

Compare within 2 ULP of the expected magnitude instead, which is still
tight enough to catch a genuinely wrong result. macOS suite goes 12 -> 9
failures; the remaining 9 are the signed-right-shift and Infinity
encoding families.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: fuzzie360

test/features/math-object.js

@@ -171,7 +171,17 @@ function sqrtABTest(mode) {
   const res = f(a,b);
   const exp = [3, 4, 5, 6, 7, 8];
 
-  assert.deepEqual(Array.from(res), exp);
+  // GLSL ES allows sqrt up to 2 ULP of error — unlike + - * / it is not
+  // required to be correctly rounded — so exact equality is not a property
+  // gpu.js can offer here. headless-gl returns 7.000000476837158 for
+  // sqrt(49.0), which is 1 ULP above 7.0 and entirely conforming.
+  Array.from(res).forEach((actual, i) => {
+    const ulp = Math.pow(2, Math.floor(Math.log2(exp[i])) - 23);
+    assert.ok(
+      Math.abs(actual - exp[i]) <= 2 * ulp,
+      `index ${i}: expected ${exp[i]} within 2 ULP, got ${actual}`
+    );
+  });
   gpu.destroy();
 }