feat(rendering): GameplayRenderer base class — occlusion for all renderers (D-170)

New GameplayRenderer extends Node2D with built-in occlusion support.
Subclasses override _gameplay_process() and _gameplay_draw() instead
of _process() and _draw() — these are skipped when a fullscreen
implant app covers gameplay.

Migrated all 5 gameplay renderers:
- CursorRenderer: hover detection + bracket drawing paused
- EntityRenderer: position lerping paused
- FogEntities: fog dot rendering paused
- SoundIndicatorRenderer: directional arrows paused
- WorldRenderer: tile/fog/entity updates paused

No more manual occlusion wiring — the base class handles everything.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client/scripts/rendering/world_renderer.gd

@@ -1,4 +1,4 @@
-extends Node2D
+extends GameplayRenderer
 
 # World renderer — manages all visual representation from GameState
 # Attached to the World node in main.tscn
@@ -14,7 +14,6 @@ extends Node2D
 #   FogOverlay (Node2D)              — z:900 fog shader (OUTSIDE FogGroup)
 
 var _last_tick: int = -1
-var _occluded: bool = false  # D-170: skip rendering when fullscreen implant app is covering us
 
 @onready var tile_renderer = $FogGroup/FloorTiles
 @onready var fog_renderer = $FogOverlay
@@ -22,19 +21,14 @@ var _occluded: bool = false  # D-170: skip rendering when fullscreen implant app
 @onready var sound_indicator_renderer = $SoundIndicators  # #126 D-018 medium-range indicators
 
 
-func _ready() -> void:
-	HudGroups.gameplay_occluded.connect(_on_gameplay_occluded)
+func _renderer_ready() -> void:
 	print("WorldRenderer: Initialized (D-049 z-stack)")
 
 
-func _on_gameplay_occluded(occluded: bool) -> void:
-	_occluded = occluded
-
-
 # Called each frame to update visuals from game state.
 # Uses tick-based invalidation — re-renders all layers when a new snapshot arrives.
 func update_from_state() -> void:
-	if _occluded:
+	if gameplay_occluded:
 		return  # D-170: skip rendering while fullscreen implant app is active
 	var tick := GameState.current_tick
 	if tick == _last_tick: