HF RL Explorer

Add support for typed MoveStruct serialization

Add support for typed MoveStruct serialization: a task in LegoFlow-SWE (Harbor dataset). Problem The MoveStruct type currently supports two representations: - Runtime – a list of values, serialized as a JSON array. - WithFields – a list of field name-value pairs, serialized as a JSON object.

The task

**Problem** The `MoveStruct` type currently supports two representations: - `Runtime` – a list of values, serialized as a JSON array. - `WithFields` – a list of field name-value pairs, serialized as a JSON object.

Part of Lego-X/LegoFlow-SWE.