Add screenshot/image upload to integ tests

[zastrowm]

We've been seeing some flakiness, I see this in the logs every time I go to investigate:

FAIL integ-browser (chromium) tests_integ/browser/agent.browser.test.ts > Agent Browser Tests with 'OpenAIModel' > handles tool invocation
Error: Test timed out in 30000ms.
If this is a long-running test, pass a timeout value as the last argument or configure it globally with "testTimeout".

Failure screenshot:

• tests_integ/browser/screenshots/agent.browser.test.ts/Agent-Browser-Tests-with--OpenAIModel--handles-tool-invocation-1.png

This will help us see those screenshots (hopefully)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.