feat: add comprehensive integration tests for auto-mode-service

- Created git-test-repo helper for managing test git repositories
- Added 13 integration tests covering:
  - Worktree operations (create, error handling, non-worktree mode)
  - Feature execution (status updates, model selection, duplicate prevention)
  - Auto loop (start/stop, pending features, max concurrency, events)
  - Error handling (provider errors, continue after failures)
- Integration tests use real git operations with temporary repos
- All 416 tests passing with 72.65% overall coverage
- Service coverage improved: agent-service 58%, auto-mode-service 44%, feature-loader 66%

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

package.json

@@ -23,6 +23,7 @@
     "lint": "npm run lint --workspace=apps/app",
     "test": "npm run test --workspace=apps/app",
     "test:headed": "npm run test:headed --workspace=apps/app",
+    "test:server": "npm run test --workspace=apps/server",
     "dev:marketing": "npm run dev --workspace=apps/marketing"
   }
 }