test: align model activity integration contract

frontend/src/shell/AppShell.session-mgmt.test.tsx

@@ -106,7 +106,7 @@ test("a failed resume keeps the panel open and does not activate the session", a
   await waitFor(() => expect(screen.getByText("Domanda originale")).toBeInTheDocument());
 });
 
-test("WIP icon toggles the Model activity panel and shows the streamed text", async () => {
+test("WIP icon toggles the Model activity panel and shows streamed reasoning", async () => {
   wrap();
   // Activate a session by opening + resuming is heavy; instead drive the store directly.
   // The WIP icon only renders with an active session, so simulate one via Resume.
@@ -114,7 +114,7 @@ test("WIP icon toggles the Model activity panel and shows the streamed text", as
   await userEvent.click(await screen.findByText("Attiva uno")); // opens docs panel
   await userEvent.click(await screen.findByRole("button", { name: /resume/i })); // active session
   const SIX_LINES = ["FIRSTLINE step one", "step two", "step three", "step four", "step five", "step six"].join("\n");
-  act(() => { useSessionStore.getState().applyEvent({ type: "text_delta", text: SIX_LINES }); });
+  act(() => { useSessionStore.getState().applyEvent({ type: "activity_delta", text: SIX_LINES }); });
   // The verbose stream stays in the (closed) left panel: its START is not shown centrally
   // (the central working indicator shows only the last 5 lines of tail, by design).
   expect(screen.queryByRole("heading", { name: /model activity/i })).not.toBeInTheDocument();