E2E Test: select video quality when publish simulcast video track.

[cloudwebrtc]

Summary

Adds an end-to-end pytest that verifies LiveKit simulcast layer switching from a Python publisher across both VP8 and H.264 codecs.

The test publishes a 1280×720 video track (rolling colored bars, generated as I420 with numpy) with simulcast=True, subscribes from a second room, and then drives the receiver through RemoteTrackPublication.set_video_quality(HIGH/MEDIUM/LOW). For each layer it asserts the decoded frames converge to roughly the expected dimensions (within ±20% tolerance, requiring 5 consecutive matching frames):

Quality	Layer	Expected
HIGH	f	1280×720
MEDIUM	h	640×360
LOW	q	320×180

Parameterized over VP8 and H264. A 5-second post-subscription warmup is included so the encoder and bandwidth estimator stabilize at the highest layer before quality switches begin.

Dependency

This test depends on livekit/rust-sdks#1052, which fixes TrackPublication.simulcasted to derive from the non-deprecated TrackInfo.codecs[*].layers field. Without that fix, modern LiveKit servers (1.10+) report info.simulcast=false (deprecated field), so set_video_quality becomes a silent no-op and this test fails on all non-HIGH layers.

This E2E test will only pass after livekit/rust-sdks#1052 is merged and a new livekit-ffi release that includes it is published and consumed by livekit-rtc. Until then, the test should be expected to fail in CI (or be marked xfail / skipped at the workflow level).

Requires

• LIVEKIT_URL, LIVEKIT_API_KEY, LIVEKIT_API_SECRET env vars (test is auto-skipped otherwise).
• numpy (already a dependency of livekit-rtc).
• livekit-ffi release containing fix: derive simulcasted from non-deprecated TrackInfo fields rust-sdks#1052.

Test plan

• pytest livekit-rtc/tests/test_change_video_quality.py -v -s passes against a current LiveKit server (verified locally on server 1.10.1 with a patched FFI dylib, both VP8 and H264).
• Test is skipped cleanly when LiveKit env vars are missing.
• No regressions in the existing tests/ suite.
• Re-run after rust-sdks#1052 is released and the FFI binary is updated.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 3 additional findings.

[cloudwebrtc]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved and pushed in commit 71ab95e. I merged origin/main into this branch and fixed the livekit-rtc/rust-sdks submodule conflict so the PR is conflict-free now.

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