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/search/conftest.py

@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import pytest
+
+from documents.search._backend import TantivyBackend
+from documents.search._backend import reset_backend
+
+if TYPE_CHECKING:
+    from collections.abc import Generator
+    from pathlib import Path
+
+    from pytest_django.fixtures import SettingsWrapper
+
+
+@pytest.fixture
+def index_dir(tmp_path: Path, settings: SettingsWrapper) -> Path:
+    path = tmp_path / "index"
+    path.mkdir()
+    settings.INDEX_DIR = path
+    return path
+
+
+@pytest.fixture
+def backend() -> Generator[TantivyBackend, None, None]:
+    b = TantivyBackend()  # path=None → in-memory index
+    b.open()
+    try:
+        yield b
+    finally:
+        b.close()
+        reset_backend()