fix(tests): add retry logic for flaky performance timing test

Fix flaky "should measure elapsed time" test that was failing due to
timer imprecision. setTimeout(10) does not guarantee exactly 10ms or
more will elapse due to OS scheduling and timer resolution.

Changes:
- Lower threshold from 10ms to 9ms to account for timer imprecision
- Add retry: 3 option to automatically retry the test on failure
- Add explanatory comment about setTimeout behavior

This test was failing intermittently with elapsed times like 9.775ms,
which is less than the 10ms threshold but within normal timer variance.

Author: jdalton

test/performance.test.ts

@@ -20,14 +20,20 @@ describe('performance', () => {
   })
 
   describe('basic performance measurements', () => {
-    it('should measure elapsed time', async () => {
-      const start = performance.now()
-      await new Promise(resolve => setTimeout(resolve, 10))
-      const end = performance.now()
-      const elapsed = end - start
-      expect(elapsed).toBeGreaterThan(0)
-      expect(elapsed).toBeGreaterThanOrEqual(10)
-    })
+    it(
+      'should measure elapsed time',
+      { retry: 3 },
+      async () => {
+        const start = performance.now()
+        await new Promise(resolve => setTimeout(resolve, 10))
+        const end = performance.now()
+        const elapsed = end - start
+        expect(elapsed).toBeGreaterThan(0)
+        // Allow for timer imprecision (9ms threshold instead of 10ms)
+        // setTimeout is not guaranteed to be exact due to OS scheduling
+        expect(elapsed).toBeGreaterThanOrEqual(9)
+      },
+    )
 
     it('should support performance.now()', () => {
       const now = performance.now()