[Testing] [Bug]: Invalid CheckpointToken on Promise Combinators

Migration from https://github.com/aws/aws-durable-execution-sdk-python-testing/issues/152

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### Expected Behavior

The Promise Combinators example from the JS SDK repository is expected to work with `sam local invoke`.

### Actual Behavior
The execution fails, there seems to be an invalid checkpoint token happening after the steps complete.

### Steps to Reproduce

Setup the SAM CLI preview, and run `samdev local invoke PromiseCombinators` from the JS SDK repo examples: https://github.com/aws/aws-durable-execution-sdk-js/tree/development/packages/aws-durable-execution-sdk-js-examples

**Note**: It would be really, really useful if the SAM CLI had a way to "grab" logs from the emulator when these things happen.

### SDK Version

0.0.1

### Python Version

3.14

### Is this a regression?

No

### Last Working Version

_No response_

### Additional Context

_No response_