feat: 搭建单元测试基础设施 — Bun test runner + 示例测试

添加 bunfig.toml 配置、test script，以及三组示例测试：
- src/utils/array.ts (intersperse, count, uniq)
- src/utils/set.ts (difference, intersects, every, union)
- packages/color-diff-napi (ansi256FromRgb, colorToEscape, detectLanguage 等)

41 tests, 0 failures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/utils/__tests__/set.test.ts

@@ -0,0 +1,63 @@
+import { describe, expect, test } from "bun:test";
+import { difference, every, intersects, union } from "../set";
+
+describe("difference", () => {
+	test("returns elements in a but not in b", () => {
+		const result = difference(new Set([1, 2, 3]), new Set([2, 3, 4]));
+		expect(result).toEqual(new Set([1]));
+	});
+
+	test("returns empty set when a is subset of b", () => {
+		expect(difference(new Set([1, 2]), new Set([1, 2, 3]))).toEqual(new Set());
+	});
+
+	test("returns a when b is empty", () => {
+		expect(difference(new Set([1, 2]), new Set())).toEqual(new Set([1, 2]));
+	});
+});
+
+describe("intersects", () => {
+	test("returns true when sets share elements", () => {
+		expect(intersects(new Set([1, 2]), new Set([2, 3]))).toBe(true);
+	});
+
+	test("returns false when sets are disjoint", () => {
+		expect(intersects(new Set([1, 2]), new Set([3, 4]))).toBe(false);
+	});
+
+	test("returns false for empty sets", () => {
+		expect(intersects(new Set(), new Set([1]))).toBe(false);
+		expect(intersects(new Set([1]), new Set())).toBe(false);
+	});
+});
+
+describe("every", () => {
+	test("returns true when a is subset of b", () => {
+		expect(every(new Set([1, 2]), new Set([1, 2, 3]))).toBe(true);
+	});
+
+	test("returns false when a has elements not in b", () => {
+		expect(every(new Set([1, 4]), new Set([1, 2, 3]))).toBe(false);
+	});
+
+	test("returns true for empty a", () => {
+		expect(every(new Set(), new Set([1, 2]))).toBe(true);
+	});
+});
+
+describe("union", () => {
+	test("combines both sets", () => {
+		const result = union(new Set([1, 2]), new Set([3, 4]));
+		expect(result).toEqual(new Set([1, 2, 3, 4]));
+	});
+
+	test("deduplicates shared elements", () => {
+		const result = union(new Set([1, 2]), new Set([2, 3]));
+		expect(result).toEqual(new Set([1, 2, 3]));
+	});
+
+	test("handles empty sets", () => {
+		expect(union(new Set(), new Set([1]))).toEqual(new Set([1]));
+		expect(union(new Set([1]), new Set())).toEqual(new Set([1]));
+	});
+});