test: add unit tests for limitNumber (#6844)

Adds a small, focused, additive unit-test file (test/limit-number.test.ts).
No existing files are modified or removed. yarn test:ci passes locally.

Co-authored-by: ytj-zuel <15623621570>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Jeniter

test/limit-number.test.ts

@@ -0,0 +1,32 @@
+// app/store/config.ts participates in an import cycle, so a static import can
+// hit a temporal-dead-zone error. Load it dynamically in beforeAll instead.
+let limitNumber: (x: number, min: number, max: number, def: number) => number;
+
+beforeAll(async () => {
+  // Warm up the import cycle in a working order before loading the target.
+  await import("../app/client/api");
+  ({ limitNumber } = await import("../app/store/config"));
+});
+
+describe("limitNumber", () => {
+  test("returns the default value for NaN input", () => {
+    expect(limitNumber(NaN, 0, 10, 5)).toBe(5);
+  });
+
+  test("clamps values below the minimum up to the minimum", () => {
+    expect(limitNumber(-3, 0, 10, 5)).toBe(0);
+  });
+
+  test("clamps values above the maximum down to the maximum", () => {
+    expect(limitNumber(99, 0, 10, 5)).toBe(10);
+  });
+
+  test("returns the value unchanged when it is within range", () => {
+    expect(limitNumber(7, 0, 10, 5)).toBe(7);
+  });
+
+  test("treats the min and max boundaries as inclusive", () => {
+    expect(limitNumber(0, 0, 10, 5)).toBe(0);
+    expect(limitNumber(10, 0, 10, 5)).toBe(10);
+  });
+});