test: fix/unflake few tests

[dgozman]

Also, descrease the number of workers on mac headed bots in an attempt to reduce flaky timeouts.

[github-actions]

Test results for "MCP"

1 failed
❌ [msedge] › mcp/files.spec.ts:106 › clicking on download link emits download @mcp-windows-latest

6295 passed, 360 skipped

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Merge workflow run.

[github-actions]

Test results for "tests 1"

1 failed
❌ [playwright-test] › hooks.spec.ts:652 › should not report error from test fixture teardown when beforeAll times out @ubuntu-latest-node24

7 flaky

⚠️ [chromium-library] › library/video.spec.ts:342 › screencast › should work for popups `@ubuntu-22.04-chromium-tip-of-tree`
⚠️ [chromium-library] › library/video.spec.ts:342 › screencast › should work for popups `@chromium-ubuntu-22.04-node24`
⚠️ [chromium-library] › library/video.spec.ts:342 › screencast › should work for popups `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/video.spec.ts:118 › screencast › should capture static page `@chromium-ubuntu-22.04-node22`
⚠️ [chromium-library] › library/video.spec.ts:342 › screencast › should work for popups `@chromium-ubuntu-22.04-node22`
⚠️ [firefox-library] › library/inspector/cli-codegen-1.spec.ts:1080 › cli codegen › should not throw csp directive violation errors `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-page] › page/page-emulate-media.spec.ts:144 › should keep reduced motion and color emulation after reload `@firefox-ubuntu-22.04-node20`

39022 passed, 846 skipped

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Merge workflow run.