chore: increase performance of legacy generators

[ovflowd]

This PR reduces make doc-only -j from 40s~ to 14s~ on my machine.

• Use WASM on the legacy generator
• JSON generator shouldn't use Shiki

That's it.

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Project	Deployment	Preview	Updated (UTC)
api-docs-tooling	Ready	Preview	Dec 4, 2025 1:14am

[codecov]

Codecov Report

❌ Patch coverage is 48.00000% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.59%. Comparing base (c77ec50) to head (495bc4c).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/utils/remark.mjs	41.17%	10 Missing ⚠️
src/generators/legacy-html-all/index.mjs	50.00%	1 Missing ⚠️
src/generators/legacy-html/index.mjs	50.00%	1 Missing ⚠️
src/generators/legacy-json/index.mjs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #505      +/-   ##
==========================================
- Coverage   74.60%   74.59%   -0.02%     
==========================================
  Files         112      112              
  Lines       10700    10713      +13     
  Branches      722      722              
==========================================
+ Hits         7983     7991       +8     
- Misses       2714     2719       +5     
  Partials        3        3              

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[Copilot]

Pull request overview

This PR improves performance of the legacy documentation generators by ~65% (from 40s to 14s) by optimizing Shiki syntax highlighting initialization and usage. The key change is splitting the getRemarkRehype() function into two variants: one without syntax highlighting (for JSON generation where highlighting isn't needed) and one with Shiki (for HTML generation where highlighting is required).

• Split getRemarkRehype() into two functions to avoid unnecessary Shiki initialization in legacy-json generator
• Enabled WebAssembly mode for Shiki highlighter via wasm: true option
• Updated legacy-html generators to use the new getRemarkRehypeWithShiki() function

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/utils/remark.mjs	Splits getRemarkRehype() into two functions: a lightweight version without Shiki and getRemarkRehypeWithShiki() with syntax highlighting support; also removes a TODO comment and reformats code
src/utils/highlighter.mjs	Adds wasm: true option to Shiki highlighter initialization for better performance and adds deprecation notice for the legacy highlighter function
src/generators/legacy-json/index.mjs	Minor whitespace formatting change
src/generators/legacy-html/index.mjs	Updates import and usage to use the new getRemarkRehypeWithShiki() function
src/generators/legacy-html-all/index.mjs	Updates import and usage to use the new getRemarkRehypeWithShiki() function

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[ovflowd]

@nodejs/web-infra can this be considered a "bug fix" and be fast-tracked? 👍 if you're ok with that.