fix(client): address PR review — invalidation, constants, tests

Review feedback from Hoshe + Tyre on PR #8:

- Extract shared TILE_SIZE to Constants class_name (Tyre #5, Hoshe #7)
- Fix tile invalidation: detect tile/visibility count changes instead
  of one-shot dirty flag, supports chunk loading (Tyre #3, #4)
- Fog dirty tracking: only re-render when visible_positions changes
- Add bounds warning for unknown tile types (Hoshe #1)
- Add player-not-found warning in GameState (Hoshe #5)
- Use Image.fill_rect() instead of pixel loops (Tyre #10)
- Document _player_pos as reserved for fog decay #113 (Tyre #6)
- Add TODO(#130) for D-033 relationship colors (Hoshe #3, Tyre #8)
- Add class_name to EntityRenderer, FogRenderer, TileRenderer
- 20 new rendering tests (D-030 Layer 1): entity lifecycle, fog
  registration, tile type mapping, snapshot completeness, constants
- 65 total tests passing, 0 failures

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

client/scripts/rendering/world_renderer.gd

@@ -8,30 +8,31 @@ extends Node2D
 @onready var fog_renderer = $FogOverlay
 @onready var entity_renderer = $Entities
 
-var _tiles_dirty: bool = true
+var _last_tile_count: int = 0
+var _last_visible_count: int = 0
 
 func _ready() -> void:
 	print("WorldRenderer: Initialized")
 
 # Called each frame to update visuals from game state
 func update_from_state() -> void:
-	# Update tiles (only when tile data changes)
+	var tile_count := GameState.visible_tiles.size()
+	var visible_count := GameState.visible_positions.size()
+
+	# Update tiles when tile data changes (new chunks loaded, D-012)
 	if tile_renderer and tile_renderer.has_method("update_tiles"):
-		if _tiles_dirty and GameState.visible_tiles.size() > 0:
+		if tile_count > 0 and tile_count != _last_tile_count:
 			tile_renderer.update_tiles(GameState.visible_tiles)
-			# Register tile positions with fog renderer for coverage
 			if fog_renderer and fog_renderer.has_method("register_tile_positions"):
 				fog_renderer.register_tile_positions(GameState.visible_tiles)
-			_tiles_dirty = false
+			_last_tile_count = tile_count
 
-	# Update fog overlay
+	# Update fog overlay when visibility changes
 	if fog_renderer and fog_renderer.has_method("update_fog"):
-		fog_renderer.update_fog(GameState.visible_positions, GameState.player_position)
+		if visible_count != _last_visible_count:
+			fog_renderer.update_fog(GameState.visible_positions, GameState.player_position)
+			_last_visible_count = visible_count
 
 	# Update entity sprites
 	if entity_renderer and entity_renderer.has_method("update_entities"):
 		entity_renderer.update_entities(GameState.visible_entities)
-
-# Mark tiles as needing re-render (call when tile data changes significantly)
-func invalidate_tiles() -> void:
-	_tiles_dirty = true