Bugfixes:
- Stop now fully rebuilds piece visuals (fixes destroyed pieces not
reappearing and lingering cargo indicators)
- Piece stock buttons use explicit selected/unselected styling instead
of ambiguous toggle behavior (teal bg + bright border when selected)
- Color dots next to stock buttons match piece colors
Features:
- Clicking a placed piece highlights its start/end cells with piece color
- Back-to-menu button ("← Menu") in top-left returns to level selector
with fade transition
- DetailPanel shows "Pion" name and has styled remove button
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Black box sim engine (commands in, events out) with 3 piece types
(Rook, Bishop, Knight), cargo transfer system with social status
priority, collision detection, and victory/defeat conditions.
57 tests covering rules, simulation, loading, and solvability.
Godot 4 presentation layer scaffolding.
