Issue: Severe performance degradation during NFA→DFA determinisation when processing large power sets.

Issue: Severe performance degradation during NFA→DFA determinisation when processing large power sets.: a task in LegoFlow-SWE (Harbor dataset). Symptom: Running fsm determinise on an NFA with many states or complex epsilon closures takes orders of magnitude longer than expected, making…

The task

**Symptom:** Running `fsm_determinise` on an NFA with many states or complex epsilon closures takes orders of magnitude longer than expected, making determinisation practically unusable for real‑world inputs.

Part of Lego-X/LegoFlow-SWE.