Replace gitui with lazygit for better git TUI experience

- Replace gitui package with lazygit in flake.nix
- Update all project templates to launch lazygit instead of gitui
- Update README documentation with lazygit features and capabilities
- Maintain same tmux workflow and window layouts

Benefits of lazygit:
- More intuitive and user-friendly interface
- Better performance and responsiveness
- Enhanced file tree navigation with git status
- Comprehensive keyboard shortcuts and help system
- Active development with regular feature updates

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

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

README.md

@@ -287,14 +287,15 @@ Edit `config/projects.nix` and run `hms` to rebuild configuration.
 
 ### 🌟 Git Visualization
 
-**Tool**: gitui
-**Purpose**: Beautiful, interactive TUI for git operations
+**Tool**: lazygit
+**Purpose**: Simple terminal UI for git commands with intuitive interface
 
-Launch with `gitui` in any git repository for:
-- Interactive commit graph visualization
-- Diff viewing and staging
-- Branch management
-- Vim-like navigation (j/k for movement, h/l for tabs)
+Launch with `lazygit` in any git repository for:
+- Interactive commit graph and branch visualization
+- Streamlined staging, committing, and diff viewing
+- Easy branch management and merging
+- File tree navigation with git status
+- Intuitive keyboard shortcuts and help system
 
 ## 📦 Included Packages