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>

apps/server/tsconfig.test.json

@@ -0,0 +1,10 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "types": ["vitest/globals", "node"],
+    "moduleResolution": "Bundler",
+    "module": "ESNext"
+  },
+  "include": ["src/**/*", "tests/**/*"],
+  "exclude": ["node_modules", "dist"]
+}