feat(frontend): build chronological activity timeline

frontend/src/stream/useSessionStream.test.tsx

@@ -22,7 +22,7 @@ test("opens an EventSource and feeds NAMED events to the store", () => {
   expect(useSessionStore.getState().pendingWidget?.id).toBe("u1");
 });
 
-test("feeds named activity_delta events to the model activity store", () => {
+test("feeds named activity_delta events to the thinking activity timeline", () => {
   renderHook(() => useSessionStream("s1"));
   const es = FakeEventSource.instances[0];
 
@@ -30,7 +30,30 @@ test("feeds named activity_delta events to the model activity store", () => {
     es.emitNamed("activity_delta", { type: "activity_delta", text: "Analizzo le ambiguità" })
   );
 
-  expect(useSessionStore.getState().activity.at(-1)?.text).toBe("Analizzo le ambiguità");
+  expect(useSessionStore.getState().activityLog.at(-1)).toMatchObject({
+    kind: "thinking",
+    text: "Analizzo le ambiguità",
+  });
+});
+
+test("feeds named activity_event events to the tool activity timeline", () => {
+  renderHook(() => useSessionStream("s1"));
+  const es = FakeEventSource.instances[0];
+
+  act(() =>
+    es.emitNamed("activity_event", {
+      type: "activity_event",
+      activity: { kind: "tool", toolCallId: "t1", toolName: "bash", status: "running" },
+    })
+  );
+
+  expect(useSessionStore.getState().activityLog).toContainEqual({
+    kind: "tool",
+    phase: null,
+    text: "bash",
+    toolCallId: "t1",
+    status: "running",
+  });
 });
 
 test("also feeds UNNAMED (default message) events to the store", () => {