Enhance React on Rails doctor with comprehensive configuration analysis

🚀 Major Enhancements:
• **Comprehensive Configuration Analysis**: Deep dive into React on Rails settings with documentation links
• **Critical Version Mismatch Detection**: Major version differences now flagged as errors (e.g., gem v16 vs npm v14)
• **Layout File Analysis**: Detects stylesheet_pack_tag and javascript_pack_tag usage across layouts
• **Server Rendering Engine Detection**: Shows ExecJS runtime (MiniRacer, Node.js, etc.) with performance notes
• **Enhanced Webpack Debugging**: Correct Shakapacker commands with advanced debugging workflow
• **JavaScript Dependencies Analysis**: Core React + build tools (webpack, babel, etc.) with clear categorization
• **Smart Breaking Changes Detection**: Only shows v16+ warnings when project actually has compatibility issues
• **Deprecated Settings Detection**: Identifies outdated config with migration guidance

🔧 Technical Improvements:
• Fixed incorrect webpack commands (removed non-existent --print-config flag)
• Added proper bundle analysis workflow with dependency checking
• Enhanced key configuration files section to include bin/dev
• Structured output with clear sections and actionable recommendations
• Improved error handling and fallback implementations

📖 Documentation & UX:
• Added doctor feature availability notice (v16.0.0+ requirement)
• Direct links to Shakapacker troubleshooting and React on Rails configuration docs
• Clear step-by-step instructions for webpack debugging and bundle analysis
• Organized output with emojis and consistent formatting

The doctor now provides developers with comprehensive, actionable diagnostics for React on Rails setup issues.

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

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

Author: justin808