Implement production vertical slice foundation

game/domain/dive/collision_observation.gd

@@ -0,0 +1,31 @@
+class_name CollisionObservation
+extends RefCounted
+
+var observation_id: StringName
+var sequence: int
+var tick_sequence: int
+var normal_impact_speed_mps: float
+
+
+func _init(
+	p_observation_id: StringName,
+	p_sequence: int,
+	p_tick_sequence: int,
+	p_normal_impact_speed_mps: float
+) -> void:
+	observation_id = p_observation_id
+	sequence = p_sequence
+	tick_sequence = p_tick_sequence
+	normal_impact_speed_mps = p_normal_impact_speed_mps
+
+
+func validation_error(expected_tick_sequence: int) -> String:
+	if observation_id.is_empty():
+		return "collision observation_id is empty"
+	if sequence < 0:
+		return "collision sequence is negative"
+	if tick_sequence != expected_tick_sequence:
+		return "collision tick sequence does not match DiveTick"
+	if not is_finite(normal_impact_speed_mps) or normal_impact_speed_mps < 0.0:
+		return "collision speed must be finite and non-negative"
+	return ""