Dedicated synthetic repro for the Claude-style camera prompt issue. The top-level page inserts a
cross-origin iframe, grants it camera; microphone via iframe permissions policy,
then asks the child frame to run enumerateDevices() followed by
getUserMedia({ video: true }).
Baseline expectation: a native browser permission prompt becomes visible and
getUserMedia can resolve after allowing it.
Hotfix expectation: if iframe media overrides are enabled, no prompt appears,
enumerateDevices() returns an empty array, and getUserMedia rejects.