Add setup.bash as main entry point for bash migration

[ooloth]

💪 What

• Files Created: setup.bash - Main entry point for dotfiles installation
• Test Coverage: test/setup/test-setup-bash.bats with 8 comprehensive tests
• Architecture: Complete bash version of setup.zsh with integrated utilities
• Quality: 8/8 tests passing, zero shellcheck warnings

🤔 Why

• Keystone PR: Main entry point validates entire bash migration architecture
• Infrastructure Integration: Uses all existing bash utilities and installation scripts
• Migration Validation: Proves that bash infrastructure can handle full setup workflow
• Professional Tooling: Enables shellcheck + bats testing for main setup script

👀 Usage

Run the bash setup:

./setup.bash

Features:

• Interactive confirmation with step list
• macOS platform validation
• Dotfiles cloning/updating with git
• Utility initialization (machine detection, dry-run, error handling)
• Prerequisite validation
• Bash installation script execution (ssh, github, homebrew, symlinks)
• Professional error handling with strict mode

👩‍🔬 How to validate

Run the test suite:

bats test/setup/test-setup-bash.bats

Expected output:

1..8
ok 1 setup.bash exists and is executable
ok 2 setup.bash sets DOTFILES environment variable
ok 3 setup.bash enables strict error handling
ok 4 setup.bash shows welcome message when run directly
ok 5 setup.bash checks for macOS platform
ok 6 setup.bash pulls latest changes when dotfiles already exist
ok 7 setup.bash loads dotfiles utilities after cloning
ok 8 setup.bash runs bash installation scripts

Verify shellcheck compliance:

shellcheck setup.bash

Test manually (dry run mode):

echo 'n' | ./setup.bash  # Should exit gracefully

Architecture Validation

This PR proves the bash migration architecture works end-to-end:

✅ Utilities Integration:

• bin/lib/machine-detection.bash - Dynamic machine detection
• bin/lib/dry-run-utils.bash - Dry-run mode support
• bin/lib/error-handling.bash - Enhanced error handling
• bin/lib/prerequisite-validation.bash - System validation

✅ Installation Scripts:

• bin/install/ssh.bash - SSH key management
• bin/install/github.bash - GitHub connectivity
• bin/install/homebrew.bash - Package management
• bin/install/symlinks.bash - Dotfiles symlinking

✅ Quality Standards:

• Strict error handling (set -euo pipefail)
• Zero shellcheck warnings (with appropriate exclusions)
• Comprehensive test coverage
• TDD implementation methodology

🔗 Related links

• Bash Migration Epic - Overall migration strategy
• PR #19: Dry-run and Error Handling Utilities - Core utilities
• PR #18: Core Utility Libraries Migration - Machine detection, prerequisites
• Current setup.zsh - Original implementation for comparison

Implementation Details

TDD Approach:

• 8 test cases covering all major functionality
• Each test validates specific behavior, not implementation details
• Comprehensive mocking for isolated testing
• Follows established bats testing patterns

Key Features:

• Interactive Flow: Welcome message → confirmation → platform check → dotfiles → utilities → installation
• Error Handling: Strict mode + enhanced error utilities + graceful failures
• Modularity: Sources utilities and installation scripts, doesn't duplicate logic
• Compatibility: Maintains same user experience as setup.zsh

Migration Benefits:

• Better Development Tools: shellcheck + bats instead of custom zsh framework
• Industry Standards: Follows bash best practices and conventions
• Easier Maintenance: Standard testing and linting tools
• Fresh Machine Friendly: Bash available everywhere, consistent behavior

Next Steps

This keystone PR enables:

1. Remaining Installation Scripts: Rust, Node.js, Neovim, Tmux, UV migrations
2. CI Integration: Shellcheck validation for all bash infrastructure
3. Framework Cleanup: Remove custom zsh test framework
4. Documentation Updates: Reflect bash-first architecture