chore: better error message when CSS selector fails to parse

[dgozman]

This updates error messages to:

• always mention "css selector";
• suggest using CSS.escape to fix it.

Unfortunately, we cannot suggest a fixed selector by applying CSS.escape(brokenToken) without updating third-party tokenizer, because things like .8abc are recognized as DimensionToken instead of DelimToken + something.

References #34320.

[github-actions]

Test results for "tests 1"

8 flaky

⚠️ [firefox-page] › tests/page/page-evaluate.spec.ts:403:3 › should throw for too deep reference chain @firefox-ubuntu-22.04-node18
⚠️ [playwright-test] › tests/ui-mode-test-update.spec.ts:83:5 › should pick new / deleted tests @ubuntu-latest-node20-1
⚠️ [webkit-library] › tests/library/browsertype-launch.spec.ts:22:3 › should reject all promises when browser is closed @webkit-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/proxy.spec.ts:93:11 › should proxy local network requests › by default › localhost @webkit-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/selector-generator.spec.ts:564:5 › selector generator › should generate multiple: noText in role @webkit-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/trace-viewer.spec.ts:149:1 › should open simple trace viewer @webkit-ubuntu-22.04-node18
⚠️ [webkit-page] › tests/page/page-set-input-files.spec.ts:147:3 › should upload large file @webkit-ubuntu-22.04-node18
⚠️ [playwright-test] › tests/ui-mode-test-watch.spec.ts:254:5 › should queue watches @windows-latest-node18-1

37590 passed, 648 skipped
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Merge workflow run.