Python: types: Handle non-text response types in AgentResponse.messages

[eavanvalkenburg]

Consider how to handle non-text response types in AgentResponse.messages. Should we allow other response types?

File: python/packages/core/agent_framework/_types.py
Location: AgentResponse.init.messages (around line ~2477)

Action: Design decision needed for handling non-text response types.

Parent issue: #3575

[eavanvalkenburg]

Non-text can be handled through Content, a change from ChatMessage to Message will also improve this, as is proposed in #3747