Protocol decoder now reads tile_kind from VisibleTile and maps it to
the client's tile type string (floor/wall/door/object). GameState
falls back to visible_tiles when the test-mode tiles array is absent,
enabling live server tile rendering.
Fix entity-to-tile alignment: server sends tile-center render coords
(tile 16 -> 16.5) but entity renderer was using raw floats, placing
entities half a tile off. Now floors the coords to get the tile index.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>