Fix compact star formatter rounding gap at 999.5k+

src/lib/format.test.ts

@@ -9,12 +9,16 @@ describe('formatCompactStars', () => {
   });
 
   it('formats four-to-six digit counts with k', () => {
-    expect(formatCompactStars(1_000)).toBe('1.0k');
+    expect(formatCompactStars(1_000)).toBe('1k');
     expect(formatCompactStars(12_345)).toBe('12.3k');
   });
 
+  it('rounds counts in the 999.5k+ window up to M instead of producing 1000k', () => {
+    expect(formatCompactStars(999_999)).toBe('1M');
+  });
+
   it('formats seven-digit counts with M', () => {
-    expect(formatCompactStars(1_000_000)).toBe('1.0M');
+    expect(formatCompactStars(1_000_000)).toBe('1M');
     expect(formatCompactStars(1_500_000)).toBe('1.5M');
   });
 });

src/lib/format.ts

@@ -1,5 +1,11 @@
+const COMPACT_FORMATTER = new Intl.NumberFormat('en', {
+  notation: 'compact',
+  maximumFractionDigits: 1,
+});
+
+// Intl emits "K" for thousands; the design uses lowercase k while keeping M.
+// Use a global regex so future locale or ICU variants that produce more than
+// one "K" still get normalized.
 export function formatCompactStars(count: number): string {
-  if (count >= 1_000_000) return `${(count / 1_000_000).toFixed(1)}M`;
-  if (count >= 1_000) return `${(count / 1_000).toFixed(1)}k`;
-  return count.toString();
+  return COMPACT_FORMATTER.format(count).replace(/K/g, 'k');
 }