Rework PDF export engine

[ThisIs-Developer]

Summary

• Reworked PDF export to use a fast print-document pipeline by default.
• Kept the existing jsPDF + html2canvas exporter as a compatibility fallback.
• Added scoped PDF print styles for better page breaks across images, Mermaid diagrams, tables, code blocks, alerts, and math.
• Improved PDF rendering parity with preview/HTML export by preserving frontmatter, reference links, Mermaid, MathJax, and image readiness.
• Synced the same PDF export behavior into the Neutralino desktop resources.
• Updated desktop lazy-loaded export libraries to resolve from local /libs assets.

Why

The previous PDF exporter captured the entire document into one large canvas and sliced it into PNG-backed PDF pages. That approach was slow for large documents, memory-heavy, and prone to layout splits.

The new default path lets the browser/desktop print engine handle pagination, which should be much faster and produce more professional PDFs with selectable text and better layout behavior.

Validation

• git diff --check
• node --check script.js
• node --check preview-worker.js
• node --check desktop-app/resources/js/script.js
• node --check desktop-app/prepare.js
• Local web smoke test confirmed the app loads, PDF controls are present, no console errors appear, and legacy PDF libraries remain unloaded before export.

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Project	Deployment	Actions	Updated (UTC)
markdown-viwer	Ready	Preview, Comment	Jun 6, 2026 7:13pm