Simulates a page whose CSP blocks our iframe. Run streamer anchor
loads the real bookmarklet.stream.src.js (HUB rewritten to this
origin) and runs it — exactly as clicking the installed bookmark would. The
anchor injects its own green overlay + canvas, opens the collar as a
host_base window, and streams the live widget back. This page just observes
(frame count, injector-ready, acks) for the L3 assertions.
Liveness: the shipped anchor drives a foreground tick, so the stream
holds ~8 fps even when you minimize the streamed popup (try it — the fps
above stays up; that's A1 working). To reproduce the OLD throttle on demand,
click Simulate background throttle: it clamps the host_base's own timer
and blocks the anchor's ticks → fps drops to ~1; click again to release → it
climbs back to ~8. See stream_frames/docs/dev_frame_liveness.md.