feat: book monthly AI-plan invoices as facts and commitments

Add ai-plan ingest that stores one current booked fact per
provider-account × plan × period. Subscriptions become recurring
commitments; usage top-ups do not. Session-level rows are rejected.

src/fin_hub/services/evaluate.py

@@ -8,7 +8,11 @@ from pathlib import Path
 from fin_hub.coupling.canon import emit_viability_alert
 from fin_hub.coupling.dev_hub import emit_resource_pressure
 from fin_hub.services.alerts import evaluate_budget_alerts
-from fin_hub.services.ledger import get_opening_balance, monthly_burn_series
+from fin_hub.services.ledger import (
+    get_opening_balance,
+    list_current_commitments,
+    monthly_burn_series,
+)
 from fin_hub.services.runway import compute_runway
 
 
@@ -30,6 +34,13 @@ def evaluate_runway(
 
     effective_currency = currency or stored_currency
     burns = monthly_burn_series(ledger_path=ledger_path, currency=effective_currency)
+    commitments = list_current_commitments(
+        ledger_path=ledger_path, currency=effective_currency
+    )
+    if not burns:
+        committed = sum((float(item.amount) for item in commitments), 0.0)
+        if committed > 0:
+            burns = [committed]
     runway = compute_runway(
         current_balance=balance,
         monthly_burns=burns,
@@ -42,6 +53,7 @@ def evaluate_runway(
         "runway": runway.as_dict(),
         "alerts": [alert.as_dict() for alert in alerts],
         "monthly_burns": burns,
+        "commitments": [item.as_dict() for item in commitments],
         "ledger_path": str(ledger_path.resolve()),
     }