4 new tests in test_fog_sprint22.gd verify BoundaryWall tiles populate boundary_positions (not visible_positions), get VIS_FORWARD without EXP_VISIBLE, stay EXP_UNEXPLORED after leaving LOS, and clear on new snapshot. Comment in tile_renderer.gd documents implicit rendering path. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>