fix: restore editor paste menu and PDF reflow

[PathGao]

Fixes #261

• let Monaco receive editor context-menu events, retaining its native Paste action
• remove stale measured fold heights during PDF printing so reflowed content occupies its actual height
• preserve collapsed fold sections in print

Tests:

• npm test
• npm run check
• cargo test --quiet

[PathGao]

@alecdotdev This branch has been rebased onto the latest #260 branch and force-pushed. Validation passed: node --test --import tsx scripts/issue261EditorPdf.test.ts, npm test, and npm run check. Please merge in this order: #254 → #258 → #260 → #266.