test(presets): use shared gitCmd helper instead of duplicate definition

Remove duplicate gitCmd function definition and import shared version from test-harness. The local definition was identical to the shared helper, just manually setting up the same environment variables. Eliminates 15 lines of duplication.

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

Author: AlbinoGeek

src/server/list-presets-tool.test.ts

@@ -1,30 +1,18 @@
 import { afterEach, describe, expect, test } from "bun:test";
-import { type ExecSyncOptionsWithStringEncoding, execFileSync } from "node:child_process";
 import { mkdirSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
 
 import { registerListPresetsTool } from "./list-presets-tool.js";
-import { captureTool, cleanupTmpPaths, mkTmpDir, writeTestGitConfig } from "./test-harness.js";
+import {
+  captureTool,
+  cleanupTmpPaths,
+  gitCmd,
+  mkTmpDir,
+  writeTestGitConfig,
+} from "./test-harness.js";
 
 afterEach(cleanupTmpPaths);
 
-function gitCmd(cwd: string, ...args: string[]): string {
-  const opts: ExecSyncOptionsWithStringEncoding = {
-    cwd,
-    encoding: "utf8",
-    env: {
-      ...process.env,
-      GIT_AUTHOR_NAME: "Test User",
-      GIT_AUTHOR_EMAIL: "test@example.com",
-      GIT_COMMITTER_NAME: "Test User",
-      GIT_COMMITTER_EMAIL: "test@example.com",
-      GIT_AUTHOR_DATE: "2025-01-01T00:00:00Z",
-      GIT_COMMITTER_DATE: "2025-01-01T00:00:00Z",
-    },
-  };
-  return execFileSync("git", args, opts);
-}
-
 function makeRepoWithPresets(): string {
   const dir = mkTmpDir("mcp-git-list-presets-test-");
   gitCmd(dir, "init", "-b", "main");