follow up to #12157. I'll try this another way.

• Create a draft pull request which creates a @ai-sdk/durable-agent package. I'm not planning on merging/releasing at this point, but having the code base in the vercel/ai repository should make it easier to iterate on.
• analyze deeply how streamText() work as a reference for buth humans and agents: how-stream-text-works.md
• Create a snapshot release: @ai-sdk/durable-agent@0.0.1
• Test @ai-sdk/durable-agentwith workflow
• Remove code duplication in @ai-sdk/durable-agent by exporting lower-level primitives from AI SDK, such as a loop iterator to externalize loop control.