breaking: add intermedia AtrulePrelude node type

[bartveneman]

breaking: make AtRule.prelude return CSSNode instead of string

Changes the .prelude getter on at-rule nodes to return CSSNode | null
instead of string | null, matching CSSTree's API and enabling traversal
of structured prelude children (media queries, layer names, etc.).

BREAKING CHANGES:

• AtRule.prelude now returns CSSNode | null instead of string | null
• Use .prelude.text to get the text representation
• Use .value for raw string when prelude parsing is disabled or unsupported
• At-rules without structured prelude parsing return null
• clone() no longer extracts prelude as a property (now part of children)

Implementation:

• Added AT_RULE_PRELUDE (40) wrapper node type
• Parser wraps parsed prelude nodes before adding to at-rule children
• Updated prelude getter to return AT_RULE_PRELUDE node or null
• Exported AT_RULE_PRELUDE constant via constants.ts
• Updated all 1107 tests to use new API

Benefits:

• Enables walking prelude children like CSSTree
• Provides structured access to media queries, layer names, etc.
• Maintains text access via .prelude.text
• Preserves arena efficiency (one wrapper per at-rule)

🤖 Generated with Claude Code

Co-Authored-By: Claude Sonnet 4.5 [email protected]

[codecov-commenter]

Codecov Report

❌ Patch coverage is 84.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.99%. Comparing base (599f11a) to head (f182c86).

Files with missing lines	Patch %	Lines
src/parse.ts	77.77%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #107      +/-   ##
==========================================
- Coverage   95.12%   94.99%   -0.13%     
==========================================
  Files          15       15              
  Lines        2583     2598      +15     
  Branches      669      674       +5     
==========================================
+ Hits         2457     2468      +11     
- Misses        126      130       +4     

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[codecov-commenter]

Bundle Report

Changes will increase total bundle size by 987 bytes (0.71%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
@projectwallace/css-parser-esm	140.57kB	987 bytes (0.71%) ⬆️

Affected Assets, Files, and Routes:

view changes for bundle: @projectwallace/css-parser-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
css-*.js	93 bytes	16.64kB	0.56%
parse.js	779 bytes	13.17kB	6.29% ⚠️
arena.js	45 bytes	10.96kB	0.41%
constants.js	53 bytes	2.08kB	2.61%
index.js	17 bytes	1.82kB	0.94%

Files in css-*.js:

• ./src/css-node.ts → Total Size: 15.78kB

Files in parse.js:

• ./src/parse.ts → Total Size: 12.31kB

Files in arena.js:

• ./src/arena.ts → Total Size: 10.04kB

Files in constants.js:

• ./src/constants.ts → Total Size: 700 bytes