fix: Eliminate unsafe manual token position updates in CSS parser

[bartveneman]

Fixes position state desynchronization bugs and consolidates position
management into safe, consistent APIs.

Changes:

1. Add Lexer.skip_whitespace_in_range() method

   • Properly maintains pos/line/column state during whitespace
     skipping
   • Centralizes whitespace/comment skipping logic in lexer
   • Eliminates code duplication across parsers

2. Replace manual backtracking with save_position/restore_position API

   • parse-selector.ts: Fix try_parse_combinator() - eliminate 9 lines
     of
     manual pos/line/column restoration
   • parse-selector.ts: Fix namespace parsing fallback paths in
     parse_type_or_namespace_selector() and
     parse_universal_or_namespace_selector()
   • parse-atrule-prelude.ts: Fix parse_single_media_query() modifier
     backtracking

3. Fix unsafe whitespace skipping methods

   • parse-atrule-prelude.ts: Replace skip_whitespace() to use
     lexer.skip_whitespace_in_range() instead of utility that only
     updates pos
   • parse-anplusb.ts: Same fix for skip_whitespace()

4. Fix unsafe position-only assignments in sub-range parsing

   • parse-atrule-prelude.ts: Fix parse_feature_value() to use
     temporary
     lexer instead of corrupting main lexer position state
   • parse-selector.ts: Fix parse_lang_identifiers() same issue

Impact:

• Fixes 4 bugs where line/column could become desynchronized from pos
• Eliminates ~30 lines of duplicated manual state management
• Makes backtracking impossible to implement incorrectly
• All 1162 tests passing

[codecov-commenter]

Bundle Report

Changes will increase total bundle size by 751 bytes (0.51%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
@projectwallace/css-parser-esm	146.7kB	751 bytes (0.51%) ⬆️

Affected Assets, Files, and Routes:

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

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
parse-*.js	137 bytes	22.98kB	0.6%
parse-*.js	-124 bytes	26.07kB	-0.47%
parse-*.js	-120 bytes	8.5kB	-1.39%
tokenize.js	858 bytes	18.5kB	4.86%

Files in parse-*.js:

• ./src/parse-atrule-prelude.ts → Total Size: 22.17kB

Files in parse-*.js:

• ./src/parse-selector.ts → Total Size: 24.68kB

Files in parse-*.js:

• ./src/parse-anplusb.ts → Total Size: 8.13kB

Files in tokenize.js:

• ./src/tokenize.ts → Total Size: 17.89kB

[codecov-commenter]

Codecov Report

❌ Patch coverage is 95.55556% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.96%. Comparing base (7c8b17e) to head (4968022).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/parse-selector.ts	87.50%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #147      +/-   ##
==========================================
+ Coverage   94.85%   94.96%   +0.10%     
==========================================
  Files          16       16              
  Lines        2704     2721      +17     
  Branches      709      712       +3     
==========================================
+ Hits         2565     2584      +19     
+ Misses        139      137       -2     

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