feat(locator): add page.getByRef

[Pavel Feldman (pavelfeldman)]

Summary

• Add page.getByRef(ref) that locates an element by its aria ref from page.ariaSnapshot({ mode: 'ai' }).
• Use it in the MCP backend and in the aria snapshot tests instead of manual aria-ref= selectors.

[github-actions]

Test results for "MCP"

8937 passed, 1489 skipped

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Merge workflow run.

[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-arm-node20`
⚠️ [chromium-library] › library/beforeunload.spec.ts:130 › should support dismissing the dialog multiple times `@realtime-time-library-chromium-linux`
⚠️ [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-library] › library/trace-viewer.spec.ts:2540 › should handle failed snapshots due to dialog `@firefox-ubuntu-22.04-node20`

52502 passed, 1270 skipped

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Merge workflow run.