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/gameplay_renderer.gd

@@ -0,0 +1,53 @@
+class_name GameplayRenderer
+extends Node2D
+## Base class for renderers that should pause when a fullscreen implant app
+## covers the gameplay view (D-170).
+##
+## Subclasses override _gameplay_process(delta) and _gameplay_draw() instead
+## of _process() and _draw(). These are only called when gameplay is visible.
+##
+## Usage:
+##   extends GameplayRenderer
+##   func _gameplay_process(delta: float) -> void: ...
+##   func _gameplay_draw() -> void: ...
+
+var gameplay_occluded: bool = false
+
+
+func _ready() -> void:
+	HudGroups.gameplay_occluded.connect(_on_gameplay_occluded)
+	_renderer_ready()
+
+
+## Override this instead of _ready() in subclasses.
+func _renderer_ready() -> void:
+	pass
+
+
+func _on_gameplay_occluded(occluded: bool) -> void:
+	gameplay_occluded = occluded
+	if occluded:
+		# Force a blank redraw so stale frames don't linger
+		queue_redraw()
+
+
+func _process(delta: float) -> void:
+	if gameplay_occluded:
+		return
+	_gameplay_process(delta)
+
+
+func _draw() -> void:
+	if gameplay_occluded:
+		return
+	_gameplay_draw()
+
+
+## Override in subclasses — called every frame when gameplay is visible.
+func _gameplay_process(_delta: float) -> void:
+	pass
+
+
+## Override in subclasses — called for draw when gameplay is visible.
+func _gameplay_draw() -> void:
+	pass