release: prepare v0.4.0 - Enhanced Edit Mode & Version Tracking

Key improvements:
- Fixed critical md-render --edit functionality that was broken
- Enhanced version tracking with git commit hash, timestamps, and local changes detection
- Comprehensive regression tests to prevent future breaks
- Repository cleanup completed

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

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

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "markitect"
-version = "0.3.0"
+version = "0.4.0"
 description = "Advanced Markdown engine for structured content"
 readme = "README.md"
 requires-python = ">=3.8"