Animation polish on top of 3.4.0-beta. Same fixes shipping as 3.5.0-alpha2:

- smooth_overlap config knob (0–1) + editor slider
- mutual gating between transition_time and smooth_overlap in editor
- full reset on structural config change; preserves view back-prop
  during interactive map edits

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>