feat: add token breakdown helpers

lib/detail-sort.test.ts

@@ -20,4 +20,16 @@ describe("sortDetailBreakdown", () => {
 
     expect(sorted.map((row) => row.name)).toEqual(["gamma", "alpha", "beta"]);
   });
+
+  test("preserves subtype fields while sorting breakdown rows", () => {
+    const rows = [
+      { name: "beta", calls: 2, total_tokens: 100, quota: 500, models: [{ name: "m2", calls: 1, total_tokens: 20, quota: 10 }] },
+      { name: "alpha", calls: 5, total_tokens: 200, quota: 300, models: [{ name: "m1", calls: 1, total_tokens: 30, quota: 20 }] },
+    ];
+
+    const sorted = sortDetailBreakdown(rows, "total_tokens", false);
+
+    expect(sorted[0].models[0].name).toBe("m1");
+    expect(rows[0].models[0].name).toBe("m2");
+  });
 });