fix(browser): preserve chat focus during agent browsing

tests/unit/agent-browser-core.test.ts

@@ -1280,7 +1280,9 @@ describe('AgentBrowserModule', () => {
     await expect(module.sendCdp({
       projectPath,
       method: 'Runtime.evaluate',
-    })).rejects.toMatchObject({ code: 'VIEWPORT_NOT_READY' });
+    })).resolves.toMatchObject({ kind: 'inline' });
+    await expect(module.readEvents({ projectPath, after: 0 })).resolves.toBeDefined();
+    await module.navigate({ projectPath, action: 'reload' });
     const reopened = await module.open({
       projectId: 'clock',
       projectPath,
@@ -1288,10 +1290,18 @@ describe('AgentBrowserModule', () => {
       visible: true,
     });
     expect(reopened).toMatchObject({
+      browserId: first.browserId,
+      generation: first.generation,
       visible: false,
       bounds: { x: 1, y: 2, width: 640, height: 480 },
     });
     expect(adapter.views[0].visible).toBe(false);
+    expect(adapter.views).toHaveLength(1);
+    await module.close(projectPath);
+    await expect(module.sendCdp({
+      projectPath,
+      method: 'Runtime.evaluate',
+    })).rejects.toMatchObject({ code: 'BROWSER_NOT_OPEN' });
   });
 
   it('waits for the matching browser generation to be presented without polling', async () => {