fix: await ensure_collection and survive partial embed failures in document sync

- ensure_collection was called without await, so the coroutine never ran
  and fresh tenants had no collection when the upsert hit Qdrant
- a single None entry from embed_batch poisoned the point batch and
  aborted the whole document upsert; failed chunks are now skipped with
  a warning (all-failed raises and the IndexResult reports failure)
- raw client.delete/client.upsert calls now go through the async wrapper
  (delete_by_filter and the new batch upsert_points method)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QbFZyDvYksazX6nYQYZ67L

src/clients/qdrant_client.py

@@ -467,6 +467,43 @@ class QdrantClientWrapper:
             logger.error(f"Failed to upsert vector: {e}", exc_info=True)
             return False
 
+    async def upsert_points(
+        self,
+        collection_name: str,
+        points: List[Dict[str, Any]]
+    ) -> int:
+        """
+        Upsert a batch of vector points in a single request.
+
+        Args:
+            collection_name: Collection name
+            points: List of {"id": str, "vector": List[float], "payload": dict}
+
+        Returns:
+            Number of points upserted
+
+        Raises:
+            Exception: If the upsert fails (callers decide how to degrade)
+        """
+        if not points:
+            return 0
+
+        structs = [
+            PointStruct(
+                id=p["id"],
+                vector=p["vector"],
+                payload=p.get("payload", {})
+            )
+            for p in points
+        ]
+
+        await self.client.upsert(
+            collection_name=collection_name,
+            points=structs
+        )
+        logger.info(f"Upserted {len(structs)} points into {collection_name}")
+        return len(structs)
+
     async def delete_by_filter(
         self,
         collection_name: str,