feat(test runner): cancel operations on test end via default abort signal

[Skn0tt]

Summary

Explores replacing the "close the context at test end to unblock in-flight operations" teardown with a default AbortSignal that fires on test end and flows into every client operation.

• The test runner sets playwright._defaultOperationSignal for the duration of the test; workerMain aborts it after afterEach with a TestEndedError(reason).
• channelOwner merges this default signal into every operation via combineSignals.
• connection rewrites the aborted error message from the TestEndedError reason, preserving the existing "Test ended." / "Test timeout of Nms exceeded." wording.
• context.close() no longer needs an explicit reason — the signal drives cancellation.

Draft / exploration — opening for discussion.

[github-actions]

Test results for "MCP"

2 failed
❌ [chromium] › mcp/annotate.spec.ts:497 › should disengage annotate mode when --annotate client disconnects @mcp-macos-latest-chromium
❌ [firefox] › mcp/cli-test.spec.ts:23 › debug test and snapshot @mcp-macos-latest-firefox

7733 passed, 1248 skipped

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Merge workflow run.

[github-actions]

Test results for "tests 1"

9 failed
❌ [chromium-library] › library/browsercontext-pages.spec.ts:128 › should not leak listeners during navigation of 20 pages @chromium-ubuntu-22.04-arm-node20
❌ [chromium-page] › page/page-goto.spec.ts:618 › should not leak listeners during 20 waitForNavigation @chromium-ubuntu-22.04-arm-node20
❌ [chromium-library] › library/browsercontext-pages.spec.ts:128 › should not leak listeners during navigation of 20 pages @chromium-ubuntu-22.04-node20
❌ [chromium-page] › page/page-goto.spec.ts:618 › should not leak listeners during 20 waitForNavigation @chromium-ubuntu-22.04-node20
❌ [firefox-library] › library/browsercontext-pages.spec.ts:128 › should not leak listeners during navigation of 20 pages @firefox-ubuntu-22.04-node20
❌ [firefox-page] › page/page-goto.spec.ts:618 › should not leak listeners during 20 waitForNavigation @firefox-ubuntu-22.04-node20
❌ [firefox-page] › page/page-request-intercept.spec.ts:269 › request.postData is not null when fetching FormData with a Blob @firefox-ubuntu-22.04-node20
❌ [webkit-library] › library/browsercontext-pages.spec.ts:128 › should not leak listeners during navigation of 20 pages @webkit-ubuntu-22.04-node20
❌ [webkit-page] › page/page-goto.spec.ts:618 › should not leak listeners during 20 waitForNavigation @webkit-ubuntu-22.04-node20

8 flaky

⚠️ [chromium-page] › page/page-request-intercept.spec.ts:269 › request.postData is not null when fetching FormData with a Blob `@frozen-time-library-chromium-linux`
⚠️ [chromium-library] › library/browsercontext-page-event.spec.ts:173 › should work with Ctrl-clicking `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-page] › page/page-request-intercept.spec.ts:269 › request.postData is not null when fetching FormData with a Blob `@realtime-time-library-chromium-linux`
⚠️ [chromium-page] › page/page-request-intercept.spec.ts:269 › request.postData is not null when fetching FormData with a Blob `@chromium-ubuntu-22.04-node24`
⚠️ [chromium-library] › library/beforeunload.spec.ts:130 › should support dismissing the dialog multiple times `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/video.spec.ts:476 › screencast › should capture static page in persistent context @smoke `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/video.spec.ts:717 › screencast › should work with video+trace `@chromium-ubuntu-22.04-node22`
⚠️ [chromium-page] › page/page-request-intercept.spec.ts:269 › request.postData is not null when fetching FormData with a Blob `@chromium-ubuntu-22.04-node22`

49499 passed, 1161 skipped

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Merge workflow run.