Fix #161: Update Grid, GridPoint, GridPointState stubs to match current API
- Grid: Update constructor (pos, size, grid_size, texture, ...) and add all
current properties (zoom, center, layers, FOV, cell events, etc.)
- Grid: Add all methods (find_path, compute_fov, add_layer, entities_in_radius, etc.)
- GridPoint: Replace incorrect properties (texture_index, solid, color) with
actual API (walkable, transparent, entities, grid_pos)
- GridPointState: Replace incorrect properties with actual API (visible, discovered, point)
- Add missing types: ColorLayer, TileLayer, FOV, AStarPath, DijkstraMap,
HeightMap, NoiseSource, BSP
Closes #161
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>