feat(js): m03 rules with fixtures and tests

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

js/test/m03-rules.test.js

@@ -0,0 +1,15 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { move, inBounds, turn, advance } from '../src/rules.js'
+import { loadFixture, freeze } from './helpers.js'
+
+const fixtureTests = (name, f) => {
+  const fx = loadFixture(name)
+  fx.cases.forEach((c) =>
+    test(`m03 ${fx.function}: ${c.name}`, () => assert.deepStrictEqual(f(...freeze(c.args)), c.expected)))
+}
+
+fixtureTests('m03-move', move)
+fixtureTests('m03-in-bounds', inBounds)
+fixtureTests('m03-turn', turn)
+fixtureTests('m03-advance', advance)