chore: docstrings und tighter upsert-test fuer qdrant store

app/qdrant_store.py

@@ -13,7 +13,11 @@ class ChunkPoint:
 
 
 def ensure_collection(client: QdrantClient, name: str, vector_size: int) -> None:
-    """Create the collection if missing. Crash if it exists with wrong dim."""
+    """Create the collection if missing. Crash if it exists with wrong dim.
+
+    Note: payload indexes are created only on initial collection creation;
+    they are not reconciled on subsequent runs.
+    """
     if not client.collection_exists(name):
         client.create_collection(
             collection_name=name,
@@ -38,6 +42,11 @@ def ensure_collection(client: QdrantClient, name: str, vector_size: int) -> None
 
 
 def upsert_chunks(client: QdrantClient, name: str, chunks: list[ChunkPoint]) -> None:
+    """Insert chunks with fresh UUID ids.
+
+    Caller is responsible for deduplication: call ``delete_by_path`` for the
+    file before re-ingesting, otherwise duplicates accumulate.
+    """
     points = [
         qm.PointStruct(id=str(uuid.uuid4()), vector=c.vector, payload=c.payload)
         for c in chunks