Support container scroll-state queries

[abdelfattahradwan]

Closes #454

Summary

CSS container scroll-state queries such as @container my-container scroll-state(scrollable: y) are valid syntax, but the parser currently treats scroll-state as invalid unless the query starts with a parenthesised size query or style(...).

This PR adds parser support for scroll-state(...) container queries while keeping the change focused to the existing @container query parsing path.

This is my first pull request here, so I followed the format of #485.

Changes

File	Change
src/parser/cssParser.ts	Recognise scroll-state(...) as a valid container query form
src/parser/cssParser.ts	Avoid consuming function-style query names like scroll-state(...) as container names
src/test/css/parser.test.ts	Add coverage for named, unnamed, nested, compound, and comma-list scroll-state queries
src/test/scss/parser.test.ts	Add SCSS parser coverage
src/test/less/parser.test.ts	Add LESS parser coverage

Test plan

• Full test suite passes with npm run test
• New test: reported @media + named @container ... scroll-state(scrollable: y) syntax parses without diagnostics
• New test: unnamed @container scroll-state(scrollable: y) parses without treating scroll-state as a container name
• Existing style(...), size-query, nested container, SCSS, and LESS parser behaviour continues to pass

[abdelfattahradwan]

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