[Lambda] Rust SDK for Durable Functions

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**Tell us about your request**

Rust SDK support for [Durable Functions](https://aws.amazon.com/about-aws/whats-new/2025/12/lambda-durable-multi-step-applications-ai-workflows/) - even basic support for just `step` and `wait` would be great, and `waitForCallback` would be a stretch goal!

**Which service(s) is this request for?**

Lambda Durable Functions

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

We use Rust exclusively in our Lambda runtimes, and would like to take advantage of Durable Functions soon.

**Are you currently working around this issue?**

We're not, we're currently blocked from adopting Durable Functions in our Rust codebases.

Comienza con el enlace de Durable Functions en el issue y define los puntos de entrada del Rust SDK necesarios para step y wait; trata waitForCallback como un objetivo adicional. Se consideraría completado contar con soporte funcional para el alcance acordado, pero este issue de roadmap no menciona archivos, pruebas ni puntos de entrada de la implementación.

Escrito por el modelo de indexación a partir del texto del issue.