Fix terminal resize bug

Fix resize handling in TerminalView component and update related tests

frontend/src/features/web/WebAgentCell.test.tsx

@@ -111,16 +111,14 @@ describe("WebAgentCell — refitSignal (ticket #61 web regression)", () => {
 
     const { rerender } = renderCell(agent, seeded.id, { refitSignal: 1 });
     await waitFor(() => expect(launchSpy).toHaveBeenCalledTimes(1));
-
-    const fitCallsAtMount = fitSpy.mock.calls.length;
-    expect(fitCallsAtMount).toBeGreaterThan(0);
+    fitSpy.mockClear();
 
     // jsdom reports a zero-size layout box, which the coalesced refit
     // deliberately skips — give the inner xterm container a real size so the
     // refit below actually reaches `fit.fit()`.
     const container = screen.getByTestId("web-agent-cell").querySelector(
-      '[data-testid="terminal-view"]',
-    )!.firstElementChild as HTMLElement;
+      '[data-testid="terminal-xterm-container"]',
+    ) as HTMLElement;
     Object.defineProperty(container, "clientWidth", { value: 400, configurable: true });
     Object.defineProperty(container, "clientHeight", { value: 200, configurable: true });
 
@@ -130,7 +128,7 @@ describe("WebAgentCell — refitSignal (ticket #61 web regression)", () => {
       </DIProvider>,
     );
 
-    await waitFor(() => expect(fitSpy.mock.calls.length).toBeGreaterThan(fitCallsAtMount));
+    await waitFor(() => expect(fitSpy).toHaveBeenCalled());
     // The whole point: refit must never relaunch the agent's PTY.
     expect(launchSpy).toHaveBeenCalledTimes(1);