Implement production vertical slice foundation

game/application/vehicle/vehicle_command.gd

@@ -0,0 +1,35 @@
+class_name VehicleCommand
+extends RefCounted
+
+var sequence: int
+var longitudinal: float
+var steering: float
+var vertical: float
+var high_thrust_active: bool
+
+
+func _init(
+	p_sequence: int,
+	p_longitudinal: float,
+	p_steering: float,
+	p_vertical: float,
+	p_high_thrust_active: bool
+) -> void:
+	sequence = p_sequence
+	longitudinal = p_longitudinal
+	steering = p_steering
+	vertical = p_vertical
+	high_thrust_active = p_high_thrust_active
+
+
+func validation_error() -> String:
+	if sequence < 0:
+		return "vehicle command sequence is negative"
+	for value: float in [longitudinal, steering, vertical]:
+		if not is_finite(value) or value < -1.0 or value > 1.0:
+			return "vehicle command axes must be finite and normalized"
+	return ""
+
+
+static func neutral(p_sequence: int) -> VehicleCommand:
+	return new(p_sequence, 0.0, 0.0, 0.0, false)