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__/file.test.ts

@@ -0,0 +1,95 @@
+import { describe, expect, test } from "bun:test";
+import {
+  convertLeadingTabsToSpaces,
+  addLineNumbers,
+  stripLineNumberPrefix,
+  pathsEqual,
+  normalizePathForComparison,
+} from "../file";
+
+describe("convertLeadingTabsToSpaces", () => {
+  test("converts leading tabs to 2 spaces each", () => {
+    expect(convertLeadingTabsToSpaces("\t\thello")).toBe("    hello");
+  });
+
+  test("only converts leading tabs", () => {
+    expect(convertLeadingTabsToSpaces("\thello\tworld")).toBe("  hello\tworld");
+  });
+
+  test("returns unchanged if no tabs", () => {
+    expect(convertLeadingTabsToSpaces("no tabs")).toBe("no tabs");
+  });
+
+  test("handles empty string", () => {
+    expect(convertLeadingTabsToSpaces("")).toBe("");
+  });
+
+  test("handles multiline content", () => {
+    const input = "\tline1\n\t\tline2\nline3";
+    const expected = "  line1\n    line2\nline3";
+    expect(convertLeadingTabsToSpaces(input)).toBe(expected);
+  });
+});
+
+describe("addLineNumbers", () => {
+  test("adds line numbers starting from 1", () => {
+    const result = addLineNumbers({ content: "a\nb\nc", startLine: 1 });
+    expect(result).toContain("1");
+    expect(result).toContain("a");
+    expect(result).toContain("b");
+    expect(result).toContain("c");
+  });
+
+  test("returns empty string for empty content", () => {
+    expect(addLineNumbers({ content: "", startLine: 1 })).toBe("");
+  });
+
+  test("respects startLine offset", () => {
+    const result = addLineNumbers({ content: "hello", startLine: 10 });
+    expect(result).toContain("10");
+  });
+});
+
+describe("stripLineNumberPrefix", () => {
+  test("strips arrow-separated prefix", () => {
+    expect(stripLineNumberPrefix("     1→content")).toBe("content");
+  });
+
+  test("strips tab-separated prefix", () => {
+    expect(stripLineNumberPrefix("1\tcontent")).toBe("content");
+  });
+
+  test("returns line unchanged if no prefix", () => {
+    expect(stripLineNumberPrefix("no prefix")).toBe("no prefix");
+  });
+
+  test("handles large line numbers", () => {
+    expect(stripLineNumberPrefix("123456→content")).toBe("content");
+  });
+});
+
+describe("normalizePathForComparison", () => {
+  test("normalizes redundant separators", () => {
+    const result = normalizePathForComparison("/a//b/c");
+    expect(result).toBe("/a/b/c");
+  });
+
+  test("resolves dot segments", () => {
+    const result = normalizePathForComparison("/a/./b/../c");
+    expect(result).toBe("/a/c");
+  });
+});
+
+describe("pathsEqual", () => {
+  test("returns true for identical paths", () => {
+    expect(pathsEqual("/a/b/c", "/a/b/c")).toBe(true);
+  });
+
+  test("returns true for equivalent paths with dot segments", () => {
+    expect(pathsEqual("/a/./b", "/a/b")).toBe(true);
+  });
+
+  test("returns false for different paths", () => {
+    expect(pathsEqual("/a/b", "/a/c")).toBe(false);
+  });
+});