feat(FN-3931): recover triage planning model session keys in triage engine

The merge fixes triage planning model session key recovery in the engine, enabling the triage agent to properly use default model keys when resuming planning sessions. Tests were added to `triage.test.ts` to assert the correct behavior.

Fusion-Task-Id: FN-3931

packages/engine/src/triage.ts

@@ -1047,6 +1047,22 @@ export class TriageProcessor {
           pluginRunner: this.options.pluginRunner,
         });
 
+        // Resolve planning model using executor-style precedence:
+        // 1. Assigned durable agent runtime model pair when complete
+        // 2. Task planning override pair
+        // 3. Planning/project/global fallbacks
+        const planningModel = resolvePlanningSessionModel(
+          task.planningModelProvider,
+          task.planningModelId,
+          settings,
+          assignedAgent?.runtimeConfig,
+        );
+
+        const planningSessionModelOptions = {
+          defaultProvider: planningModel.provider,
+          defaultModelId: planningModel.modelId,
+        };
+
         let { session } = await createResolvedAgentSession({
           sessionPurpose: "triage",
           runtimeHint: triageRuntimeHint,
@@ -1060,22 +1076,7 @@ export class TriageProcessor {
           onThinking: agentLogger.onThinking,
           onToolStart: agentLogger.onToolStart,
           onToolEnd: agentLogger.onToolEnd,
-          // Resolve planning model using executor-style precedence:
-          // 1. Assigned durable agent runtime model pair when complete
-          // 2. Task planning override pair
-          // 3. Planning/project/global fallbacks
-          ...(() => {
-            const planningModel = resolvePlanningSessionModel(
-              task.planningModelProvider,
-              task.planningModelId,
-              settings,
-              assignedAgent?.runtimeConfig,
-            );
-            return {
-              defaultProvider: planningModel.provider,
-              defaultModelId: planningModel.modelId,
-            };
-          })(),
+          ...planningSessionModelOptions,
           fallbackProvider: settings.planningFallbackProvider && settings.planningFallbackModelId
             ? settings.planningFallbackProvider
             : settings.fallbackProvider,