Add Git worktree configuration for multi-agent development with tmux

Add Git worktree configuration and best practices for multi-agent development

Our dotfiles repository needs standardized Git worktree configuration to support multi-agent AI development scenarios. Currently, we face a significant limitation: while tmux allows us to have multiple panes and windows, all panes are constrained to working on the same Git branch within a directory.

This limitation creates friction when:
- Referencing code from one branch while working on another
- Comparing implementations across branches
- Reviewing PRs while simultaneously making changes
- Multiple agents need to work on different aspects of the codebase

Git worktrees solve this by allowing multiple branches to be checked out simultaneously in different directories, which would complement tmux's pane management perfectly.

Implementation needs:
- Document worktree setup and usage patterns in README.md
- Add worktree-specific Git aliases and helper functions
- Create automation scripts for common worktree operations
- Establish conventions for worktree directory structure
- Consider integration with existing Git workflow

This will improve our development workflow when multiple agents (human or AI) need to work on different branches of the same repository simultaneously.

Review README.md and the repository’s existing Git workflow and configuration first. Define the worktree setup, directory conventions, aliases, helper functions, and automation scripts described in the issue, then verify that the documented workflow integrates with the current development process.

Written by the indexing model from the issue text.