Replace rectangular garden backgrounds with circular Garden_01.png asset,
arrange lesson buttons in a circular pattern instead of sine-wave layout,
and introduce three visual states for buttons (locked/unlocked/completed)
using the new lesson_circle.png texture. Add jellyfish mascot to gardens.
- Add new assets: Garden_01.png, lesson_circle.png, jellyfish.png
- Update garden background to use keep_aspect_centered circular display
- Implement circular lesson positioning with configurable radius
- Simplify position validation to circle-distance check
- Add layout cache versioning to invalidate old layouts
- Update boss_button.tscn to match new button design
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adrien Ufferte
