test(harness): extract shared gitInitMain helper

Move duplicated gitInitMain function to test-harness.ts and update roots.test.ts and git-parity-tool.test.ts to use shared implementation. Both files had identical definitions. Eliminates 6 lines of duplication.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: AlbinoGeek

src/server/git-parity-tool.test.ts

@@ -7,21 +7,10 @@ import { mkdirSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
 
 import { registerGitParityTool } from "./git-parity-tool.js";
-import {
-  captureTool,
-  cleanupTmpPaths,
-  gitCmd,
-  mkTmpDir,
-  writeTestGitConfig,
-} from "./test-harness.js";
+import { captureTool, cleanupTmpPaths, gitCmd, gitInitMain, mkTmpDir } from "./test-harness.js";
 
 afterEach(cleanupTmpPaths);
 
-function gitInitMain(dir: string): void {
-  gitCmd(dir, "init", "-b", "main");
-  writeTestGitConfig(dir);
-}
-
 function commitFile(dir: string, filename: string, content: string): string {
   writeFileSync(join(dir, filename), content);
   gitCmd(dir, "add", filename);

src/server/roots.test.ts

@@ -12,21 +12,10 @@ import { join } from "node:path";
 
 import { registerGitInventoryTool } from "./git-inventory-tool.js";
 import { registerGitStatusTool } from "./git-status-tool.js";
-import {
-  captureTool,
-  cleanupTmpPaths,
-  gitCmd,
-  mkTmpDir,
-  writeTestGitConfig,
-} from "./test-harness.js";
+import { captureTool, cleanupTmpPaths, gitInitMain, mkTmpDir } from "./test-harness.js";
 
 afterEach(cleanupTmpPaths);
 
-function gitInitMain(dir: string): void {
-  gitCmd(dir, "init", "-b", "main");
-  writeTestGitConfig(dir);
-}
-
 describe("workspace root resolution", () => {
   test("omitting workspaceRoot falls back to process.cwd() (which is a git repo in CI)", async () => {
     // process.cwd() during tests is the project root — a valid git repo.

src/server/test-harness.ts

@@ -193,6 +193,12 @@ export function makeRepoWithUpstream(
   return { work, remote };
 }
 
+/** Initialize a git repo with main branch and test config. */
+export function gitInitMain(dir: string): void {
+  gitCmd(dir, "init", "-b", "main");
+  writeTestGitConfig(dir);
+}
+
 /** Add a commit to a repo with specified file content. */
 export function addCommit(dir: string, file: string, content: string, message: string): void {
   writeFileSync(join(dir, file), content);