* feat(file_store): add ZvecLocalFileStore backend
- Implement ZvecLocalFileStore with native zvec collection for ANN search.
- Keep JSONL chunks as the source of truth; rebuild collection from chunks
when sidecar digest/dimension/HNSW M mismatch is detected.
- Add dedicated unit tests in tests/unit/test_zvec_file_store.py.
- Parametrize existing file_store consistency tests to cover both
LocalFileStore and ZvecLocalFileStore.
- Register the new backend in reme/components/file_store/__init__.py.
* fix(file_store): fix zvec collection sync and content validation, declare zvec dependency
