Fix loop at tactus (#1145)

* fix loopAt tactus

packages/core/pattern.mjs

@@ -2929,7 +2929,8 @@ export const splice = register(
 );
 
 export const { loopAt, loopat } = register(['loopAt', 'loopat'], function (factor, pat) {
-  return new Pattern((state) => _loopAt(factor, pat, state.controls._cps).query(state));
+  const tactus = pat.tactus ? pat.tactus.div(factor) : undefined;
+  return new Pattern((state) => _loopAt(factor, pat, state.controls._cps).query(state), tactus);
 });
 
 /**

packages/core/test/pattern.test.mjs

@@ -1248,4 +1248,9 @@ describe('Pattern', () => {
       );
     });
   });
+  describe('loopAt', () => {
+    it('maintains tactus', () => {
+      expect(s('bev').chop(8).loopAt(2).tactus).toStrictEqual(Fraction(4));
+    });
+  });
 });