feat(test-runner): support read and read-write lock modes

[Pavel Feldman (pavelfeldman)]

Summary

• lock accepts { name, mode } where mode is 'read' or 'read-write' (default); plain strings stay 'read-write'.
• Any number of 'read' holders run together, a 'read-write' holder runs alone. Read locks are not granted ahead of a queued 'read-write' job waiting for the same lock, so writers are not starved.
• A file group holds a lock in 'read-write' mode when any of its tests needs it.
• oneOf schema errors prefer the variant whose type matched, so a bad mode is reported instead of a generic type mismatch.

Fixes #42594

[github-actions]

Test results for "tests 1"

6 flaky

⚠️ [chromium-library] › library/video.spec.ts:664 › screencast › should capture full viewport `@realtime-time-library-chromium-linux`
⚠️ [chromium-library] › library/beforeunload.spec.ts:130 › should support dismissing the dialog multiple times `@chromium-ubuntu-22.04-node24`
⚠️ [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`
⚠️ [firefox-page] › page/page-emulate-media.spec.ts:144 › should keep reduced motion and color emulation after reload `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-page] › page/page-event-request.spec.ts:181 › should return response body when Cross-Origin-Opener-Policy is set `@firefox-ubuntu-22.04-node20`

50120 passed, 1235 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

7735 passed, 1228 skipped

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Merge workflow run.

[github-actions]

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

🟢 Nothing here looks caused by this PR

The one real failure — mcp/annotate.spec.ts:446 on Windows Firefox — is a long-standing flake on unrelated SHAs, and this PR only touches test-runner lock modes, which the MCP annotate flow doesn't exercise. The other 6 red squares in "tests 1" all passed on retry.

Details

This PR is scoped to the read/read-write lock feature (dispatcher.ts, testGroups.ts, test.ts, validators.ts, jsonSchema.ts, the test-locks / json-schema specs, and docs/types). None of it reaches MCP, screencast, or the annotate tooling.

Pre-existing flake / infra

• [firefox] › mcp/annotate.spec.ts:446 › should switch screencast to -s session on show --annotate (mcp-windows-latest-firefox) — pre-existing flake, Windows-Firefox only. Across the test-results DB this bot failed 68 of 2095 firefox runs (~3%) and passed the other 2027, on SHAs and PRs that have nothing to do with this change (pushes to main, plus PRs fix(network): invalidate stale network idle when requests start #42599, chore(deps): bump azure/login from 3.0.0 to 3.0.1 in the github-actions group across 1 directory #42372, docs(cli): add WebMCP skill guidance #42344, chore(trace): move trace types into isomorphic/trace/versions #42444, fix(trace): keep client paths out of remote launch options #42436, …). Never seen on chromium/webkit/msedge in any meaningful volume (0–5 failures each over ~2000 runs). Recent Windows-Firefox history for this test, oldest → newest, this PR's run being the final red:

  🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟥🟩🟩🟩🟥🟩🟩🟩🟩🟩🟩🟩🟩🟩🟥🟥🟩🟩🟥🟩🟩🟩🟩🟩🟩🟩🟥🟩🟩🟥

• The 6 entries in the "tests 1" report (video.spec.ts:664, beforeunload.spec.ts:130, two browsercontext-cookies-third-party.spec.ts, page-emulate-media.spec.ts:144, page-event-request.spec.ts:181) are all within-run flakes that passed on retry — nothing to triage, and none live anywhere near the lock code.

_{Triaged by the Playwright bot - agent run}