fix: resolve botched stash-pop conflict from 245e1280e

- scripts/lib/test-quarantine.json: remove stray <<<<<<< / ======= / >>>>>>> stash markers that broke JSON parsing
- packages/core/src/__test-utils__/vitest-setup.ts: restore \r?\n regex and \n template escapes; drop stray extra brace

scripts/lib/test-quarantine.json

@@ -11,10 +11,6 @@
       "reason": "Flake: vi.mock('node:child_process') occasionally doesn't take under workspace-concurrent runs, letting real git binary leak and report staged files unrelated to test scope (trips FileScopeViolationError). Same logic covered by real-git fixture tests in reliability-interactions/workflow-and-file-scope. FN-6206.",
       "quarantinedAt": "2026-06-10"
     },
-<<<<<<< Updated upstream
-=======
-
->>>>>>> Stashed changes
     {
       "file": "packages/engine/src/__tests__/merger-ai-cleanup.test.ts",
       "reason": "Flake observed during FN-6206 verification: `pruneExistingAiMergeWorktrees skips active-session paths` failed in full `pnpm --filter @fusion/engine test` runs while the file passed standalone, indicating suite-order/concurrency sensitivity. Follow-up FN-6207.",