feat: configurable TOC page title, cover subtitle overflow fix, blank line spacing

[Hunter-Leo]

Summary

• Configurable TOC page title: Replace hardcoded Chinese "目 录" with a configurable title that defaults to English "Contents". Supported via:
  • CLI argument --toc-title
  • Frontmatter keys toc-title or toc_title
• Cover subtitle overflow fix: Add max_w constraint to subtitle rendering on the cover page, preventing long subtitles from overflowing the page right margin
• Blank line spacing: Empty lines between paragraphs now produce vertical space instead of being silently skipped. Inside code blocks, blank lines remain preserved as-is
• TOC header font: TOC page header right-side text now uses "Serif" font (matching the document body) instead of hardcoded CJK font
• CHANGELOG.md: Add project changelog documenting all changes

Files Changed

File	Change
lovstudio-any2pdf/scripts/md2pdf.py	+15/-7 lines (2 fixes + 2 features)
lovstudio-any2pdf/SKILL.md	Add --toc-title to config reference table
README.md	Update feature list to mention TOC title
CHANGELOG.md	New file
tests/09-toc-title-custom.md	New test case for custom TOC title

Validation

• npm test — 27 test PDFs generated successfully across all themes
• --toc-title "Table of Contents" — custom title renders correctly
• Frontmatter toc-title: 目 录 — custom title renders correctly