fix: add thread-safe write lock to ChromaDB operations

src/core/ingest.py

@@ -206,12 +206,13 @@ class DocumentIngestor:
             for i, c in enumerate(chunks)
         ]
 
-        self.collection.add(
-            ids=ids,
-            embeddings=embeddings,
-            documents=texts,
-            metadatas=metadatas,
-        )
+        with self.db.write_lock:
+            self.collection.add(
+                ids=ids,
+                embeddings=embeddings,
+                documents=texts,
+                metadatas=metadatas,
+            )
 
         return len(chunks)
 
@@ -226,10 +227,11 @@ class DocumentIngestor:
     def _remove_by_source(self, file_name: str) -> None:
         """按 source_file 删除已有 chunks."""
         try:
-            existing = self.collection.get(
-                where={"source_file": file_name}
-            )
-            if existing and existing["ids"]:
-                self.collection.delete(ids=existing["ids"])
+            with self.db.write_lock:
+                existing = self.collection.get(
+                    where={"source_file": file_name}
+                )
+                if existing and existing["ids"]:
+                    self.collection.delete(ids=existing["ids"])
         except Exception:
             pass  # collection 为空时 get 可能抛异常