fix(ai): restore models after successful circuit probe

lib/ai/runtime/model-health.ts

@@ -537,7 +537,12 @@ export async function recordAiModelHealthSuccess(params: {
   if (!existing) return;
 
   const now = new Date();
-  const isObservation = isObservationPoolModel(existing);
+  // A request that started before the circuit opened can still prove the
+  // provider is reachable. Treat that success as the circuit's half-open
+  // probe instead of leaving the model disabled until the full cooldown.
+  const recoveredFromAutoDisable = existing.healthStatus === "auto_disabled";
+  const isObservation =
+    isObservationPoolModel(existing) || recoveredFromAutoDisable;
   const nextRecoverySuccessStreak = isObservation
     ? (existing.healthRecoverySuccessStreak || 0) + 1
     : 0;
@@ -547,9 +552,7 @@ export async function recordAiModelHealthSuccess(params: {
 
   const updateData: Partial<AiModel> = {
     healthStatus:
-      existing.healthStatus === "auto_disabled"
-        ? "auto_disabled"
-        : recoveredToHealthy
+      recoveredToHealthy
           ? "healthy"
           : isObservation
             ? "degraded"
@@ -566,12 +569,16 @@ export async function recordAiModelHealthSuccess(params: {
     healthObservationStartedAt: recoveredToHealthy
       ? null
       : isObservation
-        ? existing.healthObservationStartedAt
+        ? existing.healthObservationStartedAt || now
         : null,
     healthUpdatedAt: now,
     updatedAt: now,
   };
 
+  if (recoveredFromAutoDisable) {
+    updateData.isEnabled = true;
+  }
+
   if (recoveredToHealthy) {
     updateData.healthAutoDisabledAt = null;
     updateData.healthAutoDisabledReason = null;