fix(test): support multiple contexts with --debug=cli

[Dmitry Gozman (dgozman)]

Summary

• browser.bind() was called for every context created in a test, so a second browser.newContext() failed with Server is already started. Bind the browser once and reuse the session name.
• The same crash happened for the second test in a worker, so --debug=cli only ever worked for a single test with a single context. Pausing and printing the attach instructions is now done once per test.

Fixes #42485

[github-actions]

Test results for "tests 1"

4 flaky

⚠️ [chromium-library] › library/video.spec.ts:736 › screencast › should work with video+trace `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/chromium/chromium.spec.ts:179 › serviceWorker(), and fromServiceWorker() work `@chromium-ubuntu-22.04-node20`
⚠️ [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`

46302 passed, 1149 skipped

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Merge workflow run.

[github-actions]

🟢 Green — the failures are pre-existing flake and infra, not this PR

Hi, I'm the Playwright bot and I took a look at the CI failures here. None of them are caused by this change — one is a known Firefox-only flake, the other two are a transient Google Chrome mirror hiccup on the runners.

Details

This PR only touches the --debug=cli daemon binding in browserBackend.ts and adds --debug=cli tests in cli-test.spec.ts. None of the failing jobs run through that code path.

Pre-existing flake / infra

• [firefox] › mcp/cli-devtools.spec.ts:138 › request* and response* commands support --filename — Firefox-only flake. The list.match(/… \[POST\] …\/api =>/) returns null when the POST request hasn't landed in the requests list yet. Across the test-results DB this test failed 4 of 716 Firefox runs (+2 more rescued on retry), and 0 of ~2900 runs on chrome/chromium/webkit/msedge — it's flaked on unrelated PRs feat(locator): introduce locator.visible() #42479, chore: remove experimental component testing #42168, test: roll stable-test-runner to 1.63.0-alpha-2026-08-03 #42091 and on push runs aca9de8d/974edd3f. The test uses plain cli/server, not --debug=cli, so the diff can't reach it.

• ubuntu-latest - chrome and ubuntu-22.04 (chromium - Node.js 22) — both died at npx playwright install --with-deps after ~40s with E: Failed to fetch https://dl.google.com/linux/chrome-stable/deb/…/Packages.gz File has unexpected size (1410 != 1412). Mirror sync in progress?. That's a transient Google apt-mirror sync, pure infra, nothing to do with the diff. A re-run should clear both.

_{Triaged by the Playwright bot - agent run}

[github-actions]

Test results for "MCP"

8301 passed, 1371 skipped

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Merge workflow run.