Durable Objects in Dynamic Workers: Give each AI-generated app its own database

Introduced Durable Object Facets, a beta feature allowing Dynamic Workers to load and instantiate Durable Object classes dynamically. This enables AI-generated applications to have persistent state by composing Durable Objects with Dynamic Workers, where each facet gets its own isolated SQLite database. Provided a complete example of an AppRunner Durable Object that loads and runs agent-generated Durable Object code as a facet.