Standarlize content block for PlanReActPlanner and BuiltInPlanner

[perfectspr]

LangChain 1.0 provides a standard representation for message content that works across providers.
ADK has PlanReActPlanner and BuiltInPlanner, their output is raw text , need further parsing, can we also provide a standard way to do this?

[{'type': 'reasoning', 'id': 'rs_abc123', 'reasoning': 'summary 1'},
 {'type': 'reasoning', 'id': 'rs_abc123', 'reasoning': 'summary 2'},
 {'type': 'text', 'text': '...', 'id': 'msg_abc123'}]

https://docs.langchain.com/oss/python/releases/langchain-v1#standard-content-blocks
https://docs.langchain.com/oss/python/langchain/messages#standard-content-blocks