feat(sites): typed dive site definition with placements and routes

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

game/domain/sites/site_route.gd

@@ -0,0 +1,21 @@
+class_name SiteRoute
+extends Resource
+
+@export var route_id: StringName
+@export var waypoints_m := PackedVector3Array()
+@export var maximum_depth_m: float = 0.0
+
+
+func validation_error() -> String:
+	if route_id.is_empty():
+		return "route id is empty"
+	if waypoints_m.size() < 2:
+		return "route needs at least two waypoints"
+	if not is_finite(maximum_depth_m) or maximum_depth_m <= 0.0:
+		return "route maximum depth must be positive"
+	for waypoint: Vector3 in waypoints_m:
+		if not (is_finite(waypoint.x) and is_finite(waypoint.y) and is_finite(waypoint.z)):
+			return "route waypoints must be finite"
+		if -waypoint.y > maximum_depth_m:
+			return "route waypoint exceeds the route maximum depth"
+	return ""