Variable dropUnusedTransformConst

dropUnusedTransform: Fix = ...

Auto-fix for TRANSFORM_UNUSED — destroys a SceneTransform with nothing in its mesh-parent chain. Unlike SceneMaterial / SceneTexture, SceneTransform.destroy doesn't guard against mesh references — unusedResources is the precondition, not the SDK. The fix double-checks (no mesh references the transform, no live child transforms reference it) before destroying, so a stale issue lands as {fixed: false} rather than corrupting live mesh refs.

Idempotent: returns {fixed: false} when the transform is already destroyed, missing, or has live referencers.