Improve React on Rails documentation for v16 and coding agents

## New Documentation
- **troubleshooting-build-errors.md**: Comprehensive guide for webpack/build issues
  - Missing routes file error patterns and solutions
  - ProvidePlugin module resolution troubleshooting
  - Environment setup dependencies and workarounds
  - Agent-friendly diagnostic scripts and auto-fixes

- **coding-agents-guide.md**: Structured workflows for AI coding agents
  - Version compatibility matrix
  - Installation and upgrade workflows with error detection
  - Auto-fix strategies for common issues
  - Emergency procedures and rollback guidance

## Updated Documentation
- **upgrading-react-on-rails.md**:
  - Removed js:export from upgrade steps (it's a setup issue, not upgrade-specific)
  - Focused troubleshooting on actual upgrade-related issues
  - Added reference to comprehensive build errors guide

- **getting-started.md**: Updated to use react_on_rails v16.0.0
- **home.md**: Added troubleshooting guide to navigation

## Key Improvements
- Separated setup/installation issues from upgrade-specific issues
- Provided agent-friendly automation and error detection
- Enhanced troubleshooting with actionable solutions
- Improved documentation discoverability

These improvements make react_on_rails documentation more comprehensive
and accessible for both human developers and AI coding agents.

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

Co-Authored-By: Claude <[email protected]>

Author: justin808