release: bump version to 0.5.0 with clean TDD-driven editor

This release represents a major milestone in MarkiTect's evolution, featuring a complete rewrite of the editor system using test-driven development principles and clean object-oriented architecture.

Key highlights:
- Clean TDD-driven editor architecture with Section/SectionManager/DOMRenderer classes
- Multiple concurrent section editing with intelligent section splitting
- Four-layer content management system (original, current, pending, editing)
- Enhanced status dialog with repository info and version tracking
- Comprehensive testing framework with separation of concerns
- Elegant slide-in control panel and intelligent auto-sizing textarea
- Complete legacy editor system replacement

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

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

markitect/__version__.py

@@ -11,7 +11,7 @@ from pathlib import Path
 from typing import Optional
 
 # Base version from pyproject.toml
-__version__ = "0.4.0"
+__version__ = "0.5.0"
 
 def get_git_commit_hash() -> Optional[str]:
     """Get the current git commit hash if available."""