Fix critical bugs: real-time preview, toolbar functions, and file opening

Version 1.5.7 - Bug Fix Release
Fixed Issues:
- Real-time preview updates: Preview pane now updates instantly while typing
- Toolbar markdown functions: All toolbar buttons now work correctly
  * Bold, Italic, Code, Link text wrapping
  * Heading, List, Quote line prefixes
  * Table insertion
- File opening: Fixed file loading via menu and double-click association
- Cross-platform path handling for Windows backslashes
Technical Changes:
- Added direct input event listeners to editor textareas
- Implemented wrapSelection() and insertAtLineStart() helper methods
- Fixed IPC communication between main and renderer processes
- Improved event delegation for multi-tab support
🤖 Generated with [Claude Code](https://claude.com/claude-code)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pan-converter",
-  "version": "1.5.4",
+  "version": "1.5.7",
   "description": "Cross-platform Markdown editor and converter using Pandoc",
   "main": "src/main.js",
   "scripts": {