feat: migrate Node.js to new feature folder architecture

[ooloth]

Summary

Migrates Node.js installation and management to the new feature folder architecture, following the established pattern from features/ssh/, features/git/, and features/homebrew/.

Key Changes

• ✅ Self-contained feature structure - All Node.js related files in features/node/
• ✅ Bash conversion - Migrated from bin/install/node.zsh to features/node/install.bash
• ✅ Enhanced npm management - Comprehensive package management in features/node/update.bash
• ✅ No external dependencies - Removed dependencies on bin/lib/ utility files
• ✅ Comprehensive testing - 3 test files with 25+ test cases using bats framework
• ✅ Complete documentation - README with usage, troubleshooting, and migration guide

Files Added

features/node/
├── install.bash               # Node.js installation via fnm
├── update.bash               # Node.js and npm package updates  
├── utils.bash                # Node.js utility functions
├── tests/
│   ├── test-node-utils.bats         # Unit tests for utilities
│   ├── test-node-installation.bats  # Installation workflow tests
│   └── test-node-update.bats        # Update and npm management tests
└── README.md                 # Feature documentation

Migration Path

Replaces:

• bin/install/node.zsh → features/node/install.bash
• bin/update/npm.zsh → features/node/update.bash

Maintains compatibility with:

• Existing fnm configurations
• Shell auto-switching (.node-version files)
• Global npm package management

Improvements Over Legacy

1. Better error handling - Comprehensive validation and clear error messages
2. Modular design - Clear separation between installation and updates
3. Self-contained - No external library dependencies
4. Comprehensive testing - Full test coverage for all functionality
5. Enhanced npm management - Smart detection of missing/outdated packages
6. Cross-shell compatibility - Works in both bash and zsh environments

Test Plan

• Syntax validation - All bash scripts pass syntax checks
• Unit tests - 25+ test cases covering all utility functions
• Integration tests - Installation and update workflow tests
• Error handling - Tests for various failure scenarios
• Mocking - Isolated tests using fake commands
• Documentation - README covers usage, troubleshooting, and migration

Running Tests

# Run all Node.js tests
bats features/node/tests/

# Run specific test categories
bats features/node/tests/test-node-utils.bats        # Utility functions
bats features/node/tests/test-node-installation.bats # Installation workflow  
bats features/node/tests/test-node-update.bats       # Update workflow

Backwards Compatibility

This change maintains full backwards compatibility:

• Legacy scripts remain functional during transition
• Same fnm-based Node.js installation approach
• Identical npm package list and management
• No changes to shell integration or aliases

The new feature can be adopted gradually without disrupting existing workflows.