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

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

game/domain/sites/site_placement.gd

@@ -0,0 +1,35 @@
+class_name SitePlacement
+extends Resource
+
+enum Kind {
+	WRECK_TARGET,
+	WRECK_DECOY,
+	SECONDARY_ITEM,
+	DEBRIS,
+	LANDMARK,
+	VESSEL_ANCHOR,
+}
+
+@export var placement_id: StringName
+@export var kind: Kind = Kind.LANDMARK
+@export var position_m: Vector3 = Vector3.ZERO
+@export var yaw_radians: float = 0.0
+@export var footprint_m: Vector3 = Vector3.ZERO
+
+
+func is_sonar_metal() -> bool:
+	return kind in [Kind.WRECK_TARGET, Kind.WRECK_DECOY, Kind.SECONDARY_ITEM, Kind.DEBRIS]
+
+
+func validation_error() -> String:
+	if placement_id.is_empty():
+		return "placement id is empty"
+	if not (is_finite(position_m.x) and is_finite(position_m.y) and is_finite(position_m.z)):
+		return "placement position must be finite"
+	if not is_finite(yaw_radians):
+		return "placement yaw must be finite"
+	if footprint_m.x < 0.0 or footprint_m.y < 0.0 or footprint_m.z < 0.0:
+		return "placement footprint must not be negative"
+	if is_sonar_metal() and footprint_m.length_squared() == 0.0:
+		return "sonar bodies need a footprint"
+	return ""