Add Quick Start client E2E validation probe

[arussell-nvidia]

Follow-up to the Quick Start runtime validation baseline.

This draft adds a separate client validation layer that:

• starts the Quick Start runtime with the locally hosted web client and OOB hub enabled,
• launches a Chromium-based desktop/IWER client through CDP,
• clicks CONNECT, and
• requires the server-side OOB state endpoint to report streaming client metrics.

Kept as a draft while the stacked CI run proves the runner has the browser/runtime pieces needed for the fuller client E2E path.

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