feat: inference generates messages, simplify inference run events, fix encoding bug

backend/src/utils.py

@@ -9,7 +9,7 @@ def encode_value(value):
     if isinstance(value, ToolSpec):
         return value.to_openai_dict()
     elif isinstance(value, Message):
-        return {'type': value.type, 'content': encode_value(value.content)}
+        return {'role': value.role, 'content': encode_value(value.content)}
     elif isinstance(value, ToolCall):
         json = {
             'id': value.id,