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/fog_entities.gd

@@ -1,5 +1,5 @@
 class_name FogEntities
-extends Node2D
+extends GameplayRenderer
 
 ## Fog entity visualization — renders entities undergoing cognitive delay recognition
 ## in the fog layer. Between FogOverlay (z:900) and InsertOverlay (CanvasLayer 10).
@@ -50,7 +50,7 @@ var _pings: Array = []  # [{pos: Vector2, elapsed: float}]
 var _time: float = 0.0
 
 
-func _process(delta: float) -> void:
+func _gameplay_process(delta: float) -> void:
 	# Early return when idle — skip queue_redraw() when nothing to draw
 	if _entities.is_empty() and _pings.is_empty():
 		return
@@ -118,7 +118,7 @@ func update_from_state() -> void:
 		_entities.erase(eid)
 
 
-func _draw() -> void:
+func _gameplay_draw() -> void:
 	# Breathing pulse — shared across all entities
 	var pulse_t := fmod(_time, PULSE_PERIOD) / PULSE_PERIOD
 	var pulse_alpha := lerpf(PULSE_MIN_ALPHA, PULSE_MAX_ALPHA, 0.5 + 0.5 * sin(pulse_t * TAU))