fix(client): address PR #54 round 2 — stale comments, D-076 test, GROUND_FLOOR const

Remove stale smoothing re-enable comments from main.gd (Hoshe #1).
Add DIALOGUE_MAX_WIDTH=640 regression test (Hoshe #2).
Extract GROUND_FLOOR const in tile_renderer (Tyre #3).
Clean up entity_renderer migration comment (Hoshe #3).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/scripts/rendering/tile_renderer.gd

@@ -12,6 +12,7 @@ extends TileMapLayer
 #   (4,0) = reset_plate — amber (#502)
 
 const TILE_SIZE: int = Constants.TILE_SIZE
+const GROUND_FLOOR: int = 0  # Server floor level for ground — filter target in update_tiles()
 
 enum TileType { FLOOR = 0, WALL = 1, DOOR = 2, OBJECT = 3, RESET_PLATE = 4 }
 
@@ -78,10 +79,10 @@ func update_tiles(tiles: Array) -> void:
 		if not tile_data.has("x") or not tile_data.has("y") or not tile_data.has("type"):
 			continue
 
-		# Floor-level filter: only render tiles at floor level 0 (ground).
-		# Floor level 1+ tiles are for upper floors (future multi-floor nodes).
+		# Floor-level filter: only render tiles at ground floor.
+		# Upper floor tiles (level 1+) are for future multi-floor nodes.
 		var tile_z: int = tile_data.get("z", 0)
-		if tile_z != 0:
+		if tile_z != GROUND_FLOOR:
 			continue
 
 		var tile_type_str: String = tile_data.type