Support dotted layer names in @layer at-rule prelude parsing

[bartveneman]

Summary

This PR adds support for parsing dotted layer names (e.g., a.b.c) in CSS @layer at-rule prelude declarations, allowing nested layer references to be properly recognized and preserved.

Key Changes

• Enhanced layer name parsing: Modified parse_layer_names() to recognize and preserve dotted notation in layer names by consuming consecutive . and <ident> tokens that immediately follow the initial identifier with no whitespace gaps
• Whitespace sensitivity: Implemented strict position checking to ensure dots separated by whitespace are not glued to layer names (e.g., a. b parses as two separate names)
• Token imports: Added TOKEN_DELIM import to support dot token detection
• String utilities: Added CHAR_PERIOD constant for dot character code comparison
• Comprehensive test coverage: Added four new test cases covering:
  • Dotted layer names mixed with simple names in comma-separated lists
  • Deeply nested dotted layer names (e.g., d.e.f)
  • Whitespace-separated dots not being attached to names
  • Improved assertion specificity for existing dotted layer name test

Implementation Details

The parser now uses a lookahead mechanism with position save/restore to safely attempt consuming dot-identifier segments. It validates that:

1. The next token is a TOKEN_DELIM with character code matching CHAR_PERIOD
2. The dot immediately follows the previous token (no whitespace gap)
3. An identifier immediately follows the dot (no whitespace gap)

If any condition fails, the parser restores the previous position and stops consuming segments, allowing the comma separator or end of prelude to be processed normally.

https://claude.ai/code/session_01R9GWUSxhM3VVAWVFs9F5bG

[github-actions]

⚠️ Duplicate Dependencies (found: 35, threshold: 1)

📦 Package	📋 Versions
tinybench	2 versions root@ @vitest/coverage-v8@4.1.9 vitest@4.1.9 tinybench@2.9.0 root@ tinybench@6.0.2
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js-tokens	2 versions root@ @vitest/coverage-v8@4.1.9 ast-v8-to-istanbul@1.0.0 js-tokens@10.0.0 root@ tailwindcss@2.2.19 cosmiconfig@7.1.0 parse-json@5.2.0 @babel/code-frame@7.27.1 js-tokens@4.0.0
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@rolldown/binding-wasm32-wasi	2 versions root@ @vitest/coverage-v8@4.1.9 ... vite@8.0.16 rolldown@1.0.3 @rolldown/binding-wasm32-wasi@1.0.3 root@ tsdown@0.22.3 rolldown@1.1.2 @rolldown/binding-wasm32-wasi@1.1.2
obug	2 versions root@ @vitest/coverage-v8@4.1.9 obug@2.1.1 root@ tsdown@0.22.3 obug@2.1.3
picomatch	2 versions root@ tailwindcss@2.2.19 chokidar@3.6.0 anymatch@3.1.3 picomatch@2.3.2 root@ @vitest/coverage-v8@4.1.9 vitest@4.1.9 @vitest/mocker@4.1.9 vite@8.0.16 picomatch@4.0.4
postcss-value-parser	2 versions root@ tailwindcss@2.2.19 reduce-css-calc@2.1.8 postcss-value-parser@3.3.1 root@ tailwindcss@2.2.19 autoprefixer@10.4.23 postcss-value-parser@4.2.0
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rolldown	2 versions root@ @vitest/coverage-v8@4.1.9 vitest@4.1.9 @vitest/mocker@4.1.9 vite@8.0.16 rolldown@1.0.3 root@ tsdown@0.22.3 rolldown@1.1.2
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@rolldown/binding-openharmony-arm64	2 versions root@ @vitest/coverage-v8@4.1.9 ... vite@8.0.16 rolldown@1.0.3 @rolldown/binding-openharmony-arm64@1.0.3 root@ tsdown@0.22.3 rolldown@1.1.2 @rolldown/binding-openharmony-arm64@1.1.2
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@rolldown/binding-win32-x64-msvc	2 versions root@ @vitest/coverage-v8@4.1.9 ... vite@8.0.16 rolldown@1.0.3 @rolldown/binding-win32-x64-msvc@1.0.3 root@ tsdown@0.22.3 rolldown@1.1.2 @rolldown/binding-win32-x64-msvc@1.1.2
tinyexec	2 versions root@ @vitest/coverage-v8@4.1.9 vitest@4.1.9 tinyexec@1.1.2 root@ tsdown@0.22.3 tinyexec@1.2.4

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⚠️ Package Size Increase

📦 Package	📏 Base Size	📏 Source Size	📈 Size Change
@projectwallace/css-parser	41 kB	41.1 kB	+78 B