P05-02: 全費目と資金区分：表金・裏金、維持費未払い、仕入れ、人件費、元本、利息、税の帳簿への接続（原 P05-02 の完了の条件）

scripts/economy/facility_upkeep_settlement.gd

@@ -65,6 +65,33 @@ func settle(period: Dictionary, economy: EconomyService) -> Dictionary:
 	return {&"ok": true, &"replayed": false, &"receipt": receipt.duplicate(true), &"transaction_id": transaction_id}
 
 
+## Whole Gold that settling these closed periods would owe (arrears included),
+## planned with no cash; -1 if a period is invalid or already settled. Nothing changes.
+func preview_debt(periods: Array) -> int:
+	var arrears := _arrears.duplicate()
+	var fractions := _fractions.duplicate()
+	var last_end := int(_receipts[-1].period.period_end) if not _receipts.is_empty() else -1
+	var candidate := FacilityUpkeepSettlement.new()
+	for raw: Variant in periods:
+		if not raw is Dictionary:
+			return -1
+		var canonical := _parse_period(raw)
+		if canonical.is_empty() or (last_end >= 0 and canonical.period_start != last_end):
+			return -1
+		candidate._arrears = arrears
+		candidate._fractions = fractions
+		var plan := candidate._plan(canonical, 0)
+		if not plan[&"ok"]:
+			return -1
+		arrears = plan.arrears
+		fractions = plan.fractions
+		last_end = canonical.period_end
+	var debt := 0
+	for amount: int in arrears.values():
+		debt += amount
+	return debt
+
+
 func get_arrears_through(minute: int) -> int:
 	var low := 0
 	var high := _receipts.size()