Fix print null errors and add main process logging to renderer console

- Added null checks for toolbar, tab-bar, status-bar before accessing .style
- Prevents TypeError when elements don't exist
- Added executeJavaScript to send main process logs to renderer console
- Now we can see main process state in DevTools
- Print should now work without errors

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

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

test-double-click.md

@@ -0,0 +1,12 @@
+# Test Double-Click File Opening
+
+This is a test file to verify double-click functionality.
+
+## Features to Test
+- File should load automatically
+- Content should display in editor
+- Tab should show filename
+- Preview should render markdown
+
+**This text should be bold**
+*This text should be italic*