Implement production vertical slice foundation

game/domain/rules/dive_upgrade_effects.gd

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+class_name DiveUpgradeEffects
+extends RefCounted
+
+var battery_capacity_bonus_kwh: float
+var oxygen_capacity_bonus_l: float
+var hull_integrity_bonus: float
+var certified_depth_bonus_m: float
+var battery_consumption_multiplier: float
+var collision_damage_multiplier: float
+var pressure_damage_multiplier: float
+
+
+func _init(
+	p_battery_capacity_bonus_kwh: float = 0.0,
+	p_oxygen_capacity_bonus_l: float = 0.0,
+	p_hull_integrity_bonus: float = 0.0,
+	p_certified_depth_bonus_m: float = 0.0,
+	p_battery_consumption_multiplier: float = 1.0,
+	p_collision_damage_multiplier: float = 1.0,
+	p_pressure_damage_multiplier: float = 1.0
+) -> void:
+	battery_capacity_bonus_kwh = p_battery_capacity_bonus_kwh
+	oxygen_capacity_bonus_l = p_oxygen_capacity_bonus_l
+	hull_integrity_bonus = p_hull_integrity_bonus
+	certified_depth_bonus_m = p_certified_depth_bonus_m
+	battery_consumption_multiplier = p_battery_consumption_multiplier
+	collision_damage_multiplier = p_collision_damage_multiplier
+	pressure_damage_multiplier = p_pressure_damage_multiplier
+
+
+func validation_error() -> String:
+	for bonus: float in [
+		battery_capacity_bonus_kwh,
+		oxygen_capacity_bonus_l,
+		hull_integrity_bonus,
+		certified_depth_bonus_m,
+	]:
+		if not is_finite(bonus) or bonus < 0.0:
+			return "upgrade bonuses must be finite and non-negative"
+	for multiplier: float in [
+		battery_consumption_multiplier,
+		collision_damage_multiplier,
+		pressure_damage_multiplier,
+	]:
+		if not is_finite(multiplier) or multiplier <= 0.0:
+			return "upgrade multipliers must be finite and positive"
+	return ""