fix(browser): preserve chat focus during agent browsing

tests/unit/pi-product-tools.test.ts

@@ -458,6 +458,45 @@ describe('PI-090 product tools', () => {
     });
   });
 
+  it.each([false, true])('preserves the selected tab when reopening an initialized browser (visible=%s)', async (visible) => {
+    const root = await temporaryRoot('makelore-pi-browser-reuse-');
+    const initialized = {
+      browserId: 'browser-a', projectId: 'project-a', projectPath: root,
+      state: 'attached' as const, generation: 3, url: 'http://127.0.0.1:4173/', title: 'App',
+      visible, bounds: { x: 10, y: 20, width: 800, height: 600 },
+      canGoBack: false, canGoForward: false, eventCursor: 0,
+    };
+    const browser = {
+      open: vi.fn(async () => initialized),
+      waitForPresentation: vi.fn(async () => ({ ...initialized, visible: true })),
+      setDiagnostics: vi.fn(async () => initialized),
+    } as unknown as AgentBrowserModule;
+    const requestAgentBrowserPresentation = vi.fn();
+    const publishAgentBrowserState = vi.fn();
+    const tools = new PiProductTools({
+      browser,
+      attachments: new CodingAttachmentStore(path.join(root, 'attachments')),
+      bundledSkillsDir: path.resolve('resources/coding-skills'),
+      requestAgentBrowserPresentation,
+      publishAgentBrowserState,
+    });
+    const context = {
+      conversationId: 'conversation-a', runId: 'run-a', resourceId: 'browser-a',
+      projectId: 'project-a', projectPath: root, skillIds: [],
+    };
+    for (let attempt = 0; attempt < 3; attempt += 1) {
+      const result = await tools.execute('agent_browser', context, { action: 'open', url: initialized.url });
+      expect(JSON.parse(result.content[0].text)).toMatchObject({ visible, generation: 3 });
+    }
+    expect(requestAgentBrowserPresentation).not.toHaveBeenCalled();
+    expect(browser.waitForPresentation).not.toHaveBeenCalled();
+    expect(publishAgentBrowserState).toHaveBeenLastCalledWith(initialized);
+    await tools.settleRun('conversation-a', 'run-a');
+    expect(browser.setDiagnostics).toHaveBeenCalledWith({
+      projectPath: root, enabled: false, owner: 'agent:conversation-a:run-a',
+    });
+  });
+
   it('closes an agent-opened browser when presentation times out', async () => {
     const root = await temporaryRoot('makelore-pi-browser-timeout-');
     const hidden = {