Workflow run retention policy

Desired Behavior

It will be nice to have a way to configure retention period and automatically clean up workflows in terminal states without manual intervention, similar to Temporal's History Scavenger.

Possible design

// openworkflow.config.ts

export default defineConfig({
  ...,
  retention: {
    enabled: true,
    period: "30d", // shorthand, any workflow runs in terminal state past 30 days will be removed
  }
});

This is to keep it simple for now. In the future there could be more fine-grained control - e.g. frequency of this job, when to run it, customize what workflow run statuses to clean up.

I think there's a dependency on https://github.com/openworkflowdev/openworkflow/issues/246 before this can be considered.

Start by reviewing the dependency in issue #246, then inspect the configuration entry point represented by openworkflow.config.ts and defineConfig. Implement the proposed retention.period and enabled settings so workflow runs in terminal states older than the configured period are removed automatically. Done means the retention behavior can be configured without manual cleanup and matches the stated 30-day example.