fix: parse SVG as HTML tokens instead of deferring to markdown

[rohal12]

Summary

• Remove the SVG special case in the tokenizer that treated <svg>…</svg> as opaque text deferred to markdown — multi-line SVG tags were HTML-escaped because micromark doesn't recognize SVG as a type 6 HTML block tag
• Preserve original tag case in tokens so SVG camelCase elements (linearGradient, clipPath, etc.) render correctly, while keeping case-insensitive matching in the AST builder
• Add tokenizer, AST, and DOM render tests for single-line, multi-line, and nested SVG

Test plan

• Tokenizer: single-line <svg> produces correct HtmlTokens
• Tokenizer: multi-line <svg> produces correct HtmlTokens
• Tokenizer: <svg> nested inside <div> tokenizes correctly
• AST: multi-line SVG builds correct HtmlNode tree with attributes
• AST: nested SVG correctly parents under outer div
• DOM: multi-line SVG renders as actual SVG element, not escaped text
• DOM: SVG elements get correct namespace URI
• DOM: camelCase SVG elements (linearGradient) preserve tag name
• Full test suite: 975/975 pass
• Type check: clean

Closes #113

🤖 Generated with Claude Code

[github-actions]

Release preview: merging this PR will publish v0.36.2 (patch bump from v0.36.1)

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	77.53%	2609 / 3365
🔵	Statements	76.73%	2859 / 3726
🔵	Functions	67.51%	478 / 708
🔵	Branches	74.11%	1443 / 1947

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/markup/ast.ts	95%	90.78%	100%	94.25%	149-151, 160-165, 281-282
src/markup/render.tsx	90.17%	81.25%	94.11%	92.85%	72, 82, 120, 196-197, 208, 229, 230, 234-235
src/markup/tokenizer.ts	86.17%	85.44%	100%	86.13%	159-160, 203, 223-225, 259-263, 289-290, 294, 366-368, 394-396, 416, 422-424, 435, 441-443, 466-468, 492-494, 518-520, 544-546, 569-571, 614, 662-663

Generated in workflow #184 for commit 2227a63 by the Vitest Coverage Report Action