(all speculative, and not anytime soon)

• Agent<Env, State, Props> should become Agent<{state, props, ....}>
• move away from using env bindings to ctx.exports?
• inline partyserver
• remove agents/ai-chat, agents/codemode, refer to standalone packages instead
• remove ai v4 v5 code
• _persistenceHookMode and fly., onStateUpdate (use onStatePersisted instead)
• fix onError once and for all
• (more to add)