test: 添加 Utils 纯函数单元测试 (测试计划 02)

覆盖 xml, hash, stringUtils, semver, uuid, format, frontmatterParser,
file, glob, diff 共 10 个模块的纯函数测试。
json.ts 因模块加载链路过重暂跳过。
共 190 个测试用例（含已有 array/set）全部通过。

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

src/utils/__tests__/format.test.ts

@@ -0,0 +1,133 @@
+import { describe, expect, test } from "bun:test";
+import {
+  formatFileSize,
+  formatSecondsShort,
+  formatDuration,
+  formatNumber,
+  formatTokens,
+  formatRelativeTime,
+} from "../format";
+
+describe("formatFileSize", () => {
+  test("formats bytes", () => {
+    expect(formatFileSize(500)).toBe("500 bytes");
+  });
+
+  test("formats kilobytes", () => {
+    expect(formatFileSize(1536)).toBe("1.5KB");
+  });
+
+  test("formats megabytes", () => {
+    expect(formatFileSize(1.5 * 1024 * 1024)).toBe("1.5MB");
+  });
+
+  test("formats gigabytes", () => {
+    expect(formatFileSize(2 * 1024 * 1024 * 1024)).toBe("2GB");
+  });
+
+  test("removes trailing .0", () => {
+    expect(formatFileSize(1024)).toBe("1KB");
+  });
+});
+
+describe("formatSecondsShort", () => {
+  test("formats milliseconds to seconds", () => {
+    expect(formatSecondsShort(1234)).toBe("1.2s");
+  });
+
+  test("formats zero", () => {
+    expect(formatSecondsShort(0)).toBe("0.0s");
+  });
+
+  test("formats sub-second", () => {
+    expect(formatSecondsShort(500)).toBe("0.5s");
+  });
+});
+
+describe("formatDuration", () => {
+  test("formats 0 as 0s", () => {
+    expect(formatDuration(0)).toBe("0s");
+  });
+
+  test("formats seconds", () => {
+    expect(formatDuration(5000)).toBe("5s");
+  });
+
+  test("formats minutes and seconds", () => {
+    expect(formatDuration(125000)).toBe("2m 5s");
+  });
+
+  test("formats hours", () => {
+    expect(formatDuration(3661000)).toBe("1h 1m 1s");
+  });
+
+  test("formats days", () => {
+    expect(formatDuration(90000000)).toBe("1d 1h 0m");
+  });
+
+  test("hideTrailingZeros removes zero components", () => {
+    expect(formatDuration(3600000, { hideTrailingZeros: true })).toBe("1h");
+    expect(formatDuration(60000, { hideTrailingZeros: true })).toBe("1m");
+  });
+
+  test("mostSignificantOnly returns largest unit", () => {
+    expect(formatDuration(90000000, { mostSignificantOnly: true })).toBe("1d");
+    expect(formatDuration(3661000, { mostSignificantOnly: true })).toBe("1h");
+  });
+});
+
+describe("formatNumber", () => {
+  test("formats small numbers as-is", () => {
+    expect(formatNumber(900)).toBe("900");
+  });
+
+  test("formats thousands with k suffix", () => {
+    const result = formatNumber(1321);
+    expect(result).toContain("k");
+  });
+
+  test("formats millions", () => {
+    const result = formatNumber(1500000);
+    expect(result).toContain("m");
+  });
+});
+
+describe("formatTokens", () => {
+  test("removes .0 from formatted number", () => {
+    const result = formatTokens(1000);
+    expect(result).not.toContain(".0");
+  });
+
+  test("formats small numbers", () => {
+    expect(formatTokens(500)).toBe("500");
+  });
+});
+
+describe("formatRelativeTime", () => {
+  const now = new Date("2026-01-15T12:00:00Z");
+
+  test("formats seconds ago", () => {
+    const date = new Date("2026-01-15T11:59:30Z");
+    const result = formatRelativeTime(date, { now });
+    expect(result).toContain("30");
+    expect(result).toContain("ago");
+  });
+
+  test("formats minutes ago", () => {
+    const date = new Date("2026-01-15T11:55:00Z");
+    const result = formatRelativeTime(date, { now });
+    expect(result).toContain("5");
+    expect(result).toContain("ago");
+  });
+
+  test("formats future time", () => {
+    const date = new Date("2026-01-15T13:00:00Z");
+    const result = formatRelativeTime(date, { now });
+    expect(result).toContain("in");
+  });
+
+  test("handles zero difference", () => {
+    const result = formatRelativeTime(now, { now });
+    expect(result).toContain("0");
+  });
+});