refactor(filesystem): make pifs providers configurable

tests/test_metadata_generation.py

@@ -0,0 +1,30 @@
+import sys
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+if str(REPO_ROOT) not in sys.path:
+    sys.path.insert(0, str(REPO_ROOT))
+
+
+def test_metadata_generator_uses_provider_parameter():
+    from pageindex.filesystem.metadata_generation import (
+        MetadataGenerationError,
+        MetadataGenerationInput,
+        MetadataGenerator,
+    )
+
+    generator = MetadataGenerator(provider="unsupported", model="unused")
+    request = MetadataGenerationInput(
+        file_ref="file_a",
+        external_id="doc_a",
+        title="A",
+        source_path="docs/a.txt",
+        content_type="text/plain",
+        source_type=None,
+        text="hello",
+    )
+
+    with pytest.raises(MetadataGenerationError, match="unsupported metadata provider: unsupported"):
+        generator.generate(request, fields=["summary"])