Add print functionality and native PDF support (v1.7.7)

- Added Print menu item with Ctrl+P keyboard shortcut for native OS printing
- Implemented print IPC handlers in main and renderer processes
- Remapped Toggle Preview from Ctrl+P to Ctrl+Shift+P to avoid conflicts
- Added PDFKit (v0.14.0) for native PDF generation without Pandoc
- Added html2pdf.js (v0.10.1) for HTML to PDF conversion
- Enhanced CLAUDE.md with new v1.7.7 feature documentation
- Print supports cross-platform printing (Windows, macOS, Linux)

Features:
- Native print dialog with background color printing
- Professional PDF export without system dependencies
- Improved portability and offline support

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

package.json

@@ -33,9 +33,11 @@
     "codemirror": "^6.0.2",
     "dompurify": "^3.2.6",
     "electron-store": "^10.1.0",
+    "html2pdf.js": "^0.10.1",
     "highlight.js": "^11.11.1",
     "marked": "^16.2.1",
     "pdf-lib": "^1.17.1",
+    "pdfkit": "^0.14.0",
     "tslib": "^2.8.1",
     "xlsx": "^0.18.5"
   },