Feature: Replace Whoosh with tantivy search backend (#12471)

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Antoine Mérino <3023499+Merinorus@users.noreply.github.com>

src/documents/tests/conftest.py

@@ -1,5 +1,6 @@
 import shutil
 import zoneinfo
+from collections.abc import Generator
 from dataclasses import dataclass
 from pathlib import Path
 from typing import TYPE_CHECKING
@@ -92,6 +93,26 @@ def sample_doc(
     )
 
 
+@pytest.fixture()
+def _search_index(
+    tmp_path: Path,
+    settings: SettingsWrapper,
+) -> Generator[None, None, None]:
+    """Create a temp index directory and point INDEX_DIR at it.
+
+    Resets the backend singleton before and after so each test gets a clean
+    index rather than reusing a stale singleton from another test.
+    """
+    from documents.search import reset_backend
+
+    index_dir = tmp_path / "index"
+    index_dir.mkdir()
+    settings.INDEX_DIR = index_dir
+    reset_backend()
+    yield
+    reset_backend()
+
+
 @pytest.fixture()
 def settings_timezone(settings: SettingsWrapper) -> zoneinfo.ZoneInfo:
     return zoneinfo.ZoneInfo(settings.TIME_ZONE)