fix(dev-infra): skip hook setup in CI

scripts/install-lefthook.spec.ts

@@ -118,6 +118,7 @@ function createFixture(names: { main?: string; linked?: string } = {}): Fixture
   const linked = join(container, names.linked ?? 'linked')
   const env: NodeJS.ProcessEnv = {
     ...process.env,
+    CI: 'false',
     GIT_AUTHOR_EMAIL: 'hooks@example.test',
     GIT_AUTHOR_NAME: 'Hooks Test',
     GIT_COMMITTER_EMAIL: 'hooks@example.test',
@@ -187,6 +188,26 @@ function runInstaller(
 }
 
 describe('worktree-local Lefthook installer', () => {
+  it('skips hook installation when CI is true', async () => {
+    const fixture = createFixture()
+    const common = commonDirectory(fixture)
+    const missingInclude = join(fixture.container, 'missing-ci-credentials.gitconfig')
+    git(fixture, fixture.main, [
+      'config',
+      '--local',
+      'includeIf.gitdir:/github/workspace/.git.path',
+      missingInclude,
+    ])
+
+    const result = await runInstaller(fixture, fixture.main, { CI: 'true' })
+
+    expect(result.status, result.stderr).toBe(0)
+    expect(gitResult(fixture, fixture.main, ['config', '--get', 'extensions.worktreeConfig']).status).toBe(1)
+    expect(git(fixture, fixture.main, ['config', '--get', 'core.repositoryFormatVersion'])).toBe('0')
+    expect(existsSync(hooksPath(fixture, fixture.main))).toBe(false)
+    expect(existsSync(join(common, 'config.worktree'))).toBe(false)
+  })
+
   it('isolates main and linked worktrees without changing legacy common hooks', async () => {
     const fixture = createFixture()
     const common = commonDirectory(fixture)