Improve parser performance

[darthmaim]

This doubles the performance for text only inputs, and is also quite a bit faster for other markup.

Before

 ✓ test/parser.bench.ts > text only 2751ms
     name                                         hz     min      max    mean     p75     p99    p995    p999      rme  samples
   · parse                              1,394,333.70  0.0003  11.2692  0.0007  0.0005  0.0014  0.0023  0.0245  ±10.86%   697167
   · parse({ includePosition: false })  2,463,950.83  0.0002   4.1256  0.0004  0.0004  0.0009  0.0022  0.0133   ±1.97%  1231976

 ✓ test/parser.bench.ts > simple markup 1411ms
     name                                       hz     min     max    mean     p75     p99    p995    p999     rme  samples
   · parse                              362,314.67  0.0022  0.5758  0.0028  0.0027  0.0039  0.0054  0.0490  ±0.78%   181158
   · parse({ includePosition: false })  432,193.63  0.0018  2.2539  0.0023  0.0023  0.0032  0.0040  0.0385  ±1.19%   216097

 ✓ test/parser.bench.ts > complex markup 1209ms
     name                                     hz     min     max    mean     p75     p99    p995    p999     rme  samples
   · parse                              4,653.99  0.1789  3.8645  0.2149  0.2105  0.4692  0.8598  1.5449  ±2.10%     2327
   · parse({ includePosition: false })  5,739.96  0.1511  0.8865  0.1742  0.1781  0.3018  0.4014  0.7819  ±0.80%     2870

After

 ✓ test/parser.bench.ts > text only 3387ms
     name                                         hz     min     max    mean     p75     p99    p995    p999     rme  samples
   · parse                              2,695,008.51  0.0002  5.7137  0.0004  0.0003  0.0009  0.0021  0.0057  ±2.54%  1347505
   · parse({ includePosition: false })  4,138,253.35  0.0002  0.7431  0.0002  0.0003  0.0003  0.0004  0.0012  ±0.77%  2069127

 ✓ test/parser.bench.ts > simple markup 1503ms
     name                                       hz     min     max    mean     p75     p99    p995    p999     rme  samples
   · parse                              520,265.73  0.0015  0.6584  0.0019  0.0019  0.0027  0.0031  0.0208  ±0.67%   260134
   · parse({ includePosition: false })  594,701.55  0.0012  2.5628  0.0017  0.0016  0.0024  0.0033  0.0308  ±2.20%   297351

 ✓ test/parser.bench.ts > complex markup 1210ms
     name                                     hz     min     max    mean     p75     p99    p995    p999     rme  samples
   · parse                              5,785.16  0.1487  2.7702  0.1729  0.1697  0.3173  0.5834  1.2858  ±1.56%     2893
   · parse({ includePosition: false })  6,961.24  0.1218  0.8324  0.1437  0.1439  0.2086  0.2831  0.6341  ±0.73%     3481

Changes

• Don't value.slice(i) on every iteration, instead work with value[i] if possible
• Peek at the next character before using regex
• Keep track of current children in variable (instead of getting them of the stack everytime)
• Use indexOf instead of regex search to find next potential node

[Copilot]

Pull request overview

This PR optimizes the Guild Wars 2 markup parser for better performance, particularly for text-only inputs which see a ~2x improvement. The changes refactor the main parsing loop to reduce string allocations and regex operations without changing the parser's behavior.

Changes:

• Replaced the currentChildren() helper function with a tracked children variable that's updated when pushing/popping from the stack
• Optimized character-by-character processing by peeking at value[i] before doing expensive string slicing and regex matching
• Replaced regex-based search for next nodes with faster indexOf calls for < and \n characters

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/parser/src/parser.ts	Refactored main parsing loop with performance optimizations: tracks children array as variable, peeks at characters before regex matching, uses indexOf for finding next nodes
.changeset/silly-symbols-own.md	Added changeset documenting the performance improvement as a patch release

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