Function generate_sync_file 

pub fn generate_sync_file(entity: &Entity) -> (String, String)

Generate sync/{snake}_sync.rs — delta sync and merge helpers for a CRDT entity.

Only generated for entities that have at least one CRDT field. The delta struct includes fields backed by DeltaCrdt (GCounter, PNCounter, ORSet). The merge function handles all CRDT fields via state-based merge.