fix(usage): format near-million token counts as millions (#39129)

Co-authored-by: CurryMessi <curry-messi@users.noreply.github.com>

src/utils/usage-format.test.ts

@@ -12,6 +12,8 @@ describe("usage-format", () => {
     expect(formatTokenCount(999)).toBe("999");
     expect(formatTokenCount(1234)).toBe("1.2k");
     expect(formatTokenCount(12000)).toBe("12k");
+    expect(formatTokenCount(999_499)).toBe("999k");
+    expect(formatTokenCount(999_500)).toBe("1.0m");
     expect(formatTokenCount(2_500_000)).toBe("2.5m");
   });
 

src/utils/usage-format.ts

@@ -25,7 +25,12 @@ export function formatTokenCount(value?: number): string {
     return `${(safe / 1_000_000).toFixed(1)}m`;
   }
   if (safe >= 1_000) {
-    return `${(safe / 1_000).toFixed(safe >= 10_000 ? 0 : 1)}k`;
+    const precision = safe >= 10_000 ? 0 : 1;
+    const formattedThousands = (safe / 1_000).toFixed(precision);
+    if (Number(formattedThousands) >= 1_000) {
+      return `${(safe / 1_000_000).toFixed(1)}m`;
+    }
+    return `${formattedThousands}k`;
   }
   return String(Math.round(safe));
 }