fix: round negative half away from zero to match Ruby/Shopify behavior

Math.round(-2.5) returns -2 in JS (toward zero), but Ruby rounds to -3 (away from zero). Use sign-preserving abs+round to match Shopify Liquid.

Closes #871

Made-with: Cursor

src/filters/math.ts

@@ -15,5 +15,6 @@ export function round (v: number, arg = 0) {
   v = toNumber(v)
   arg = toNumber(arg)
   const amp = Math.pow(10, arg)
-  return Math.round(v * amp) / amp
+  const n = v * amp
+  return (Math.sign(n) * Math.round(Math.abs(n))) / amp
 }

test/integration/filters/math.spec.ts

@@ -68,6 +68,8 @@ describe('filters/math', function () {
     it('should return "183.36" for 183.357,2',
       () => test('{{183.357|round: 2}}', '183.36'))
     it('should convert string to number', () => test('{{"2.7"|round}}', '3'))
+    it('should round -2.5 to -3 (away from zero)', () => test('{{ -2.5 | round }}', '-3'))
+    it('should round -1.5 to -2 (away from zero)', () => test('{{ -1.5 | round }}', '-2'))
   })
   describe('times', function () {
     it('should return "6" for 3,2', () => test('{{ 3 | times: 2 }}', '6'))