Add Linkedom Node target

[pedraal]

Summary

This MR aims to offer a more performant target for node env and make some global performance improvements.
The current defuddle/node uses JSDOM which is quite slow vs Linkedom. The former being already used for Cloudflare Worker target.

Changes

• Create a defuddle/linkedom export target, inspired of the defuddle/node and what is done in website/src/convert.ts to patch missing APIs in Linkedom.
• Precompile regexes to avoid recompiling them on every parse calls
• Scope post processing to the selected main content element

Benchmark

Here are the results I've observed by running defuddle/node vs defuddle/linkedom on a Macbook pro M3 with node v24.12.0

Running 58 fixtures × 5 runs each…
..........................................................

Fixture	JSDOM (ms)	linkedom (ms)	speedup
codeblocks--mintlify	35.9	11.3	3.18x
codeblocks--rehype-pretty-code	12.4	2.4	5.09x
codeblocks--rockthejvm.com:articles:kotlin-101-type-classes	18.7	4.1	4.57x
codeblocks--stripe	55.4	17.0	3.26x
comments--news.ycombinator.com:item?id=12345678	36.8	8.9	4.12x
comments--old.reddit.com:r:test:comments:abc123:test_post	35.0	8.8	3.99x
elements--complex-tables	22.7	5.5	4.16x
elements--data-table	14.0	3.2	4.34x
elements--embedded-videos	16.2	2.2	7.32x
elements--farsi-zwnj	10.0	2.3	4.36x
elements--javascript-links	8.8	1.8	4.89x
elements--lazy-image	35.8	11.6	3.08x
elements--nbsp-handling	6.3	1.4	4.66x
elements--whitespace-newlines	7.4	1.5	4.79x
footnotes--maggieappleton.com-xanadu-patterns	112.6	31.7	3.55x
general--12gramsofcarbon.com:p:ilyas-30-papers-to-carmack-vlaes	92.3	30.7	3.00x
general--apnews-link-enhancement	7.7	1.3	6.09x
general--appendix-heading	9.5	1.9	4.92x
general--cp4space-jordan-algebra	21.6	5.6	3.86x
general--daringfireball.net:2025:02:the_iphone_16e	54.4	13.8	3.94x
general--developer.mozilla.org:en-US:docs:Web:JavaScript:Reference:Global_Objects:Array	12.0	2.7	4.44x
general--github.com-issue-56	117.0	43.3	2.70x
general--github.com:test-owner:test-repo:pull:42	18.5	4.5	4.11x
general--lesswrong.com:s:N7nDePaNabJdnbXeE:p:vJFdjigzmcXMhNTsx	277.1	64.5	4.29x
general--multi-article-portfolio	12.2	3.0	4.11x
general--news.ycombinator.com:item?id=12345678	24.1	5.9	4.07x
general--obsidian.md:blog:verify-obsidian-sync-encryption	28.7	6.6	4.36x
general--react-streaming-ssr	6.4	1.0	6.22x
general--scp-wiki.wikidot.com-scp-9935	20.7	6.4	3.21x
general--stephango.com-buy-wisely	22.8	5.8	3.94x
general--substack-app	58.4	24.9	2.35x
general--tailwind-hidden-blog-index	25.5	6.2	4.09x
general--wikipedia	86.4	26.1	3.31x
general--www.figma.com:blog:introducing-codex-to-figma	50.7	15.5	3.26x
general--x.com-article-2026-02-13	225.3	82.9	2.72x
general--x.com-article	9.5	2.3	4.13x
hidden--nodes	6.6	1.4	4.90x
hidden--visibility	9.3	1.5	6.32x
issues--106-menu-id	8.2	1.6	5.07x
issues--114-leading-hr	8.2	2.0	4.20x
issues--120-dhammatalks-footnotes	29.4	8.1	3.64x
issues--131-category-links	8.8	1.8	4.95x
issues--132-hero-class	10.5	1.6	6.70x
issues--136-time-element	8.5	1.6	5.33x
issues--141-arxiv-equation-tables	31.9	7.2	4.40x
issues--142-arxiv-multi-citations	21.3	5.8	3.64x
issues--143-arxiv-cross-references	12.5	2.7	4.56x
issues--144-arxiv-footnote-marks	17.2	4.6	3.70x
math--katex-centraliser	165.8	57.4	2.89x
math--katex	58.8	17.6	3.33x
math--mathjax-tex-scripts	9.0	2.0	4.55x
math--mathjax	206.2	64.0	3.22x
math--temml	43.8	13.1	3.34x
math--wikipedia-mathml	22.6	5.1	4.46x
scoring--related-posts-byline	12.9	3.7	3.45x
scoring--table-with-links	22.7	5.4	4.20x
table-layout--paulgraham.com-makersschedule	18.6	4.8	3.89x
table-layout--single-column	15.1	2.9	5.27x
Total	2356.3	684.6	3.44x

Testing

• A tests/linkedom.test.ts is added to ensure it is running over existing fixtures (even though it is not checking that the content is the expected one) and that it is preserving the same API as defuddle/node target