feat: add agent runtime info tracking with model detection from rollout files

packages/app/src/utils/extract-agent-model.ts

@@ -0,0 +1,9 @@
+import type { Agent } from "@/stores/session-store";
+
+export function extractAgentModel(agent?: Agent | null): string | null {
+  if (!agent) return null;
+  const runtimeModel = agent.runtimeInfo?.model;
+  return typeof runtimeModel === "string" && runtimeModel.trim().length > 0
+    ? runtimeModel.trim()
+    : null;
+}