Fix custom usage script summaries (#3129)

Co-authored-by: Zihao Han <hanhan3344@users.noreply.github.com>

tests/utils/usageDisplay.test.ts

@@ -0,0 +1,49 @@
+import { describe, expect, it } from "vitest";
+import { formatUsageDataSummary } from "@/utils/usageDisplay";
+
+const labels = {
+  invalid: "Invalid",
+  remaining: "Remaining:",
+  used: "Used:",
+};
+
+describe("formatUsageDataSummary", () => {
+  it("formats used percentage when remaining is omitted", () => {
+    expect(
+      formatUsageDataSummary(
+        {
+          planName: "Coco OpenRouter",
+          used: 55,
+          total: 100,
+          unit: "%",
+        },
+        labels,
+      ),
+    ).toBe("[Coco OpenRouter] Used: 55%");
+  });
+
+  it("formats remaining when present", () => {
+    expect(
+      formatUsageDataSummary(
+        {
+          planName: "Balance",
+          remaining: 12.5,
+          unit: "USD",
+        },
+        labels,
+      ),
+    ).toBe("[Balance] Remaining: 12.50 USD");
+  });
+
+  it("formats invalid results without requiring quota fields", () => {
+    expect(
+      formatUsageDataSummary(
+        {
+          isValid: false,
+          invalidMessage: "Unauthorized",
+        },
+        labels,
+      ),
+    ).toBe("Unauthorized");
+  });
+});