chore(bidi): scale screencast frames in the browser

[Holger Benl (hbenl)]

Fixes "screencast.start delivers frames via onFrame callback" in library/screencast.spec.ts.
Note that this PR regresses the test "onFrame receives viewport size" in the same file: the onFrame callback receives the scaled image's dimensions instead of the viewport dimensions. But I think it's worth making this change anyway for the performance improvement of not sending unscaled images over the protocol.
In the long run we want to move away from using browsingContext.captureScreenshot for screencasts (see w3c/webdriver-bidi#1134), we'll make sure that this will also include the viewport dimensions.

[github-actions]

Test results for "tests 1"

5 flaky

⚠️ [chromium-library] › library/video.spec.ts:762 › screencast › should work with video+trace `@chromium-ubuntu-22.04-node22`
⚠️ [firefox-library] › library/browsercontext-cookies-third-party.spec.ts:257 › third party 'Partitioned;' cookies `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-library] › library/browsercontext-cookies-third-party.spec.ts:470 › top level 'Partitioned;' cookie and same origin iframe `@firefox-ubuntu-22.04-node20`
⚠️ [playwright-test] › ui-mode-trace.spec.ts:715 › should indicate current test status `@windows-latest-node22`
⚠️ [playwright-test] › ui-mode-trace.spec.ts:827 › should update state on subsequent run `@windows-latest-node22`

52279 passed, 1255 skipped

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Merge workflow run.

[github-actions]

Test results for "MCP"

1 failed
❌ [firefox] › mcp/annotate.spec.ts:446 › should switch screencast to -s session on show --annotate @mcp-windows-latest-firefox

8750 passed, 1480 skipped

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Merge workflow run.

[github-actions]

Hi, I'm the Playwright bot and I took a first look at the CI failures here.

🟢 The one failure is a pre-existing flake

[firefox] › mcp/annotate.spec.ts:446 on Windows fails regularly on main and unrelated PRs; this PR doesn't reach it.

Details

The only failing test in the latest report is an MCP test on mcp-windows-latest-firefox. The PR changes BiDi screencast scaling (bidiPage.ts, BiDi protocol types) and removes the BiDi-only getFFmpegVideoFilterArgs hook, so videoRecorder.ts for non-BiDi pages keeps the same pad/crop filter it used before. The MCP [firefox] project runs the stock Juggler Firefox, not BiDi, so none of the changed code is exercised differently.

Pre-existing flake / infra

• [firefox] › mcp/annotate.spec.ts:446 › should switch screencast to -s session on show --annotate — in the test-results DB, on mcp-windows-latest-firefox it failed 37 of 396 runs (~9%), including pushes to main (e.g. run 35785374310, run 35661458547) and unrelated PRs (fix(chromium): report numpad location on keyup #42913, fix(mcp): rebind page-registered WebMCP tools when the tab or frame changes #42821, feat(trace-viewer): show screencast frames during playback #42751). On macOS and Ubuntu it gets rescued by a retry about 1 run in 8.

_{Triaged by the Playwright bot - agent run}