feat(client): Sprint 6 Touch — z-layer pipeline, cursor, fog, interactions, inventory, stance, radial

Three-scope z-layer rendering pipeline (D-049): world z:0-900 inside
CanvasGroup, insert overlay CanvasLayer 10, UI CanvasLayer 20, modal
CanvasLayer 30. Y-sort contract enforced (entities z_index=0). Reserved
ranges for VFX, airborne, lower floors documented in constants.gd.

Sprint 6 client tickets:
- #429: Cursor state machine — 4 states, 150ms transitions (D-056)
- #430: Fog shader rebuild — 5-layer fragment shader, animated noise (D-059)
- #432: Entity interaction list — vertical multi-verb, insert-styled (D-057)
- #433: World radial menu — 2 spokes, drag-release + click-click (D-058)
- #438: Inventory UI — 3x3 grid, 40x40px, 1-9 hotkeys (D-065)
- #439: Stance indicator — color-coded HUD, C/X keybinds (D-053)

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

client/scripts/rendering/world_renderer.gd

@@ -2,16 +2,25 @@ extends Node2D
 
 # World renderer — manages all visual representation from GameState
 # Attached to the World node in main.tscn
-# Render order (scene tree): TileMapLayer -> FogOverlay -> Entities
+#
+# D-049 Z-level rendering pipeline (z-layer-gap-analysis.md):
+#   FogGroup (CanvasGroup) composites world content:
+#     FloorTiles (TileMapLayer)      — z:0 ground plane
+#     FloorObjects (Node2D)          — z:10 cosmetic detail (placeholder)
+#     YSortGroup (Node2D, y_sort)    — z:100 furniture + entities (all z:0 relative)
+#       Furniture (Node2D, y_sort)   — z:0 placed objects (placeholder)
+#       Entities (Node2D, y_sort)    — z:0 entity sprites (D-033 colors)
+#     Overhead (Node2D)              — z:300 ceiling/upper structure (placeholder)
+#   FogOverlay (Node2D)              — z:900 fog shader (OUTSIDE FogGroup)
 
-@onready var tile_renderer = $TileMapLayer
+@onready var tile_renderer = $FogGroup/FloorTiles
 @onready var fog_renderer = $FogOverlay
-@onready var entity_renderer = $Entities
+@onready var entity_renderer = $FogGroup/YSortGroup/Entities
 
 var _last_tick: int = -1
 
 func _ready() -> void:
-	print("WorldRenderer: Initialized")
+	print("WorldRenderer: Initialized (D-049 z-stack)")
 
 # Called each frame to update visuals from game state.
 # Uses tick-based invalidation — re-renders all layers when a new snapshot arrives.
@@ -25,12 +34,10 @@ func update_from_state() -> void:
 	if tile_renderer and tile_renderer.has_method("update_tiles"):
 		if GameState.visible_tiles.size() > 0:
 			tile_renderer.update_tiles(GameState.visible_tiles)
-			if fog_renderer and fog_renderer.has_method("register_tile_positions"):
-				fog_renderer.register_tile_positions(GameState.visible_tiles)
 
-	# Update fog overlay from visibility data
+	# Update fog overlay — shader-based, reads from FogState autoload
 	if fog_renderer and fog_renderer.has_method("update_fog"):
-		fog_renderer.update_fog(GameState.visible_positions, GameState.player_position)
+		fog_renderer.update_fog()
 
 	# Update entity sprites
 	if entity_renderer and entity_renderer.has_method("update_entities"):