New updates to A2UI and Flutter’s GenUI package

The Flutter team has released updates to the genui package (v0.9.0) and the A2UI protocol. Key changes include architectural decoupling that removes the ContentGenerator abstraction in favor of distinct Engine, Transport, and Facade layers, giving developers direct control over LLM connections. The update also shifts from a 'Structured Output First' to a 'Prompt First' approach, injecting UI schemas directly into system prompts via a new PromptBuilder utility. Breaking changes include A2UI protocol renames (beginRendering to createSurface, flat component definitions), class renames dropping the GenUi prefix, and a new genai_primitives package for shared messaging types. Migration guidance from v0.7.0 to v0.9.0 is provided.