fix(core): translate Google GenAI text blocks to v1 (#33699)

Author: ccurme

libs/core/langchain_core/messages/block_translators/google_genai.py

@@ -458,6 +458,8 @@ def _convert_to_v1_from_genai(message: AIMessage) -> list[types.ContentBlock]:
                 if outcome is not None:
                     server_tool_result_block["extras"]["outcome"] = outcome
                 converted_blocks.append(server_tool_result_block)
+            elif item_type == "text":
+                converted_blocks.append(cast("types.TextContentBlock", item))
             else:
                 # Unknown type, preserve as non-standard
                 converted_blocks.append({"type": "non_standard", "value": item})