feat(audio): add wall contact cue

Game/scripts/ship.gd

@@ -197,6 +197,7 @@ signal thrust_changed(thrust_percent: float)
 signal angular_velocity_changed(angular_speed: float)
 signal heading_changed(heading_degrees: float)
 signal ball_contact(intensity: float, world_position: Vector3)
+signal wall_contact(intensity: float)
 
 # Performance optimization - track last emitted values to avoid unnecessary signals
 var _last_speed: float = -1.0
@@ -415,6 +416,8 @@ func is_turbo_active() -> bool:
 
 
 func _on_body_entered(body: Node) -> void:
+	if body is StaticBody3D:
+		wall_contact.emit(clampf(linear_velocity.length() / maxf(max_speed, 0.001), 0.0, 1.0))
 	if not body is Ball:
 		return
 	var relative_speed := (linear_velocity - (body as Ball).linear_velocity).length()