Bone Flow Realtime Preview #001 Build 1.0.11

Change scope
- FIT remains uniform zoom.
- Initial automatic FIT now enables vertical compaction as well as width fitting.
- Explicit FIT recalculates the same compact height.
- Preview-only and Editor+Preview both use the same path.
- Runtime renderer, Shape, Joint, parser and definition sources are unchanged.

Required visible result
- A horizontal flow no longer keeps the former fixed 420/760px preview height after initial render.
- The preview panel height follows rendered flow bounds plus FIT padding.
