fix(electron): enable screenshot-on-failure for Electron apps

[Glisa060]

Summary

• Track Electron contexts in Playwright._allContexts() so the test runner's SnapshotRecorder can capture screenshots from Electron windows on test failure
• Fire runAfterCreateBrowserContext instrumentation hook for Electron contexts to enable tracing/artifact collection
• Clean up tracking on Electron app close
• Add e2e test verifying screenshot: 'only-on-failure' produces test-failed-1.png for Electron apps

cc @pavelfeldman

[Glisa060]

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