Fix CDP monitor test navigation readiness

[rgarcia]

Summary

• wait for Target.createTarget navigation to commit to the expected stub URL before treating the page as ready
• apply the same deterministic readiness condition to the lifecycle/reconnect and worker network-capture regressions
• preserve the existing injection, worker, telemetry, and reconnect assertions without adding sleeps or operation retries

Root cause

Target.createTarget({url: stub.URL}) can return while the new target still exposes its initial about:blank document. Both tests considered document.readyState === "complete" && window.__kernelEventInjected === true sufficient, but the monitor can inject into that initial document before the requested navigation commits.

On unmodified origin/main (f33a66e), the exact CI command reproduced TestNetworkCaptureFromWorkers locally. All worker cases executed against the opaque initial document:

• dedicated worker: '/worker.js' is not a valid URL
• shared worker: access denied to origin 'null'
• service worker: navigator.serviceWorker was undefined

The linked CI run also timed out at the identical predicate in TestTelemetryConnectionOwnershipAndReconnect. Requiring location.href === stub.URL + "/" prevents the initial document from satisfying readiness and synchronizes both tests on the intended committed document.

Failing run: https://github.com/kernel/kernel-images/actions/runs/34779734931/job/103785618145

Validation

From server/:

• 10 consecutive independent invocations passed (10/10, one fresh go test process each):

  KERNEL_CDPMONITOR_CHROME_E2E=1 go test -race ./lib/cdpmonitor -run '^(TestNetworkCapture|TestTelemetryConnection)' -count=1 -v

  Runs completed from 2026-09-14T09:38:08Z through 2026-09-14T09:41:12Z.
• focused lifecycle + workers browser regression passed:

  KERNEL_CDPMONITOR_CHROME_E2E=1 go test -race ./lib/cdpmonitor -run '^(TestTelemetryConnectionOwnershipAndReconnect|TestNetworkCaptureFromWorkers)$' -count=1 -v

• normal race tests passed:

  go test -race ./lib/cdpmonitor ./lib/browsersurface ./lib/cdpclient

• git diff --check passed

Checklist

• A link to the related failure is included above.
• The proposed change and validation are described above.