Fix outlineWidth calc validation

[cyphercodes]

What changed / motivation ?

Allow outlineWidth to use the same width validator as border widths, which accepts CSS length expressions like calc(...) while continuing to reject numeric strings such as "10".

Added a focused regression test covering direct outlineWidth: 'calc(...)' and nested pseudoselector value syntax.

Linked PR/Issues

Fixes #1690

Additional Context

Tests run:

• npm test --workspace @stylexjs/eslint-plugin -- --runTestsByPath __tests__/stylex-valid-styles-test.js --runInBand --coverage=false
• npx prettier --check packages/@stylexjs/eslint-plugin/src/reference/cssProperties.js packages/@stylexjs/eslint-plugin/__tests__/stylex-valid-styles-test.js
• npx eslint packages/@stylexjs/eslint-plugin/src/reference/cssProperties.js packages/@stylexjs/eslint-plugin/__tests__/stylex-valid-styles-test.js
• git diff --check
• npm run build --workspace @stylexjs/eslint-plugin

Note: yarn install --frozen-lockfile installed dependencies and began the repo postinstall build, but the full monorepo build timed out while building docs after @stylexjs/eslint-plugin had built successfully.

Pre-flight checklist

• I have read the contributing guidelines
  Contribution Guidelines
• Performed a self-review of my code

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
stylex	Skipped		Jun 2, 2026 3:35am