fix(5.1): Remove unused _MAX_SKILL_NAME_LENGTH import from evolver.py

Opus 4.6 review flagged: constant only used inside _sanitize_skill_name
which moved to evolution/models.py. Dead import removed.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Brian Krafft

openspace/skill_engine/evolver.py

@@ -29,7 +29,6 @@
 from openspace.utils.logging import Logger
 
 from .evolution.models import (
-    _MAX_SKILL_NAME_LENGTH,
     EvolutionContext,
     EvolutionTrigger,
     _sanitize_skill_name,