Widen chunk() type to accept None, add test for None guard

haiku_rag_slim/haiku/rag/chunkers/base.py

@@ -15,7 +15,7 @@ class DocumentChunker(ABC):
     """
 
     @abstractmethod
-    async def chunk(self, document: "DoclingDocument") -> list["Chunk"]:
+    async def chunk(self, document: "DoclingDocument | None") -> list["Chunk"]:
         """Split a document into chunks with metadata.
 
         Args:

haiku_rag_slim/haiku/rag/chunkers/docling_local.py

@@ -162,7 +162,7 @@ class DoclingLocalChunker(DocumentChunker):
 
         return result
 
-    async def chunk(self, document: "DoclingDocument") -> list[Chunk]:
+    async def chunk(self, document: "DoclingDocument | None") -> list[Chunk]:
         """Split the document into chunks with metadata.
 
         Extracts structured metadata from each DocChunk including:

haiku_rag_slim/haiku/rag/chunkers/docling_serve.py

@@ -129,7 +129,7 @@ class DoclingServeChunker(DocumentChunker):
 
         return result.get("chunks", [])
 
-    async def chunk(self, document: "DoclingDocument") -> list[Chunk]:
+    async def chunk(self, document: "DoclingDocument | None") -> list[Chunk]:
         """Split the document into chunks with metadata via docling-serve.
 
         Extracts structured metadata from the API response including:

tests/test_chunker.py

@@ -55,6 +55,13 @@ async def test_local_chunker(qa_corpus: list[dict[str, str]]):
     assert abs(total_tokens - original_tokens) <= original_tokens * 0.1
 
 
+@pytest.mark.asyncio
+async def test_local_chunker_none_document():
+    """Test DoclingLocalChunker returns empty list for None document."""
+    chunker = DoclingLocalChunker()
+    assert await chunker.chunk(None) == []
+
+
 @pytest.mark.asyncio
 async def test_local_chunker_runs_off_event_loop_thread():
     """Chunking is CPU-bound; verify it runs in a worker thread."""