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

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

@@ -0,0 +1,22 @@
+import { describe, expect, it } from "vitest";
+import type { Agent } from "@/stores/session-store";
+import { extractAgentModel } from "./extract-agent-model";
+
+describe("extractAgentModel", () => {
+  it("returns runtime model when present", () => {
+    const agent = {
+      runtimeInfo: { model: "gpt-5.2-codex" },
+    } as Partial<Agent> as Agent;
+
+    expect(extractAgentModel(agent)).toBe("gpt-5.2-codex");
+  });
+
+  it("returns null when runtime model missing even if config model is set", () => {
+    const agent = {
+      model: "gpt-5.1-codex",
+      runtimeInfo: {},
+    } as Partial<Agent> as Agent;
+
+    expect(extractAgentModel(agent)).toBeNull();
+  });
+});