Introducing AI Transport v0.5.0: durable execution with Steps

What this post added

Introduced the 'Steps' concept for AI Transport, providing stable `stepId`s to ensure idempotency for publishable units of output during retries in durable execution frameworks. Added `run.adoptRun()` and `run.load()` to allow new processes to seamlessly join and continue an existing run. Provided specific integrations for Temporal (`stepIdFor`) and Vercel Workflows (using `getStepMetadata`) to leverage their retry mechanisms and stable step IDs.