Add SSR conversion docs and demo scaffolds

MIGRATION_PR_STRATEGY.md

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+# Migration Strategy: Inertia Rails → Shakapacker + React on Rails
+
+## Repository Setup
+
+### Fork & Clone
+```bash
+# Fork the official repository
+gh repo fork inertia-rails/react-starter-kit --clone --remote-name upstream
+
+# Or if you want it in a specific location
+cd ~/projects  # or wherever you keep projects
+gh repo fork inertia-rails/react-starter-kit --clone
+cd react-starter-kit
+```
+
+## PR Strategy: Incremental Migration
+
+### Phase 1: Foundation PRs (Non-Breaking)
+
+#### PR #1: Add Shakapacker alongside Vite
+**Branch:** `add-shakapacker-support`
+**Changes:**
+- Add `shakapacker` gem (keep `vite_rails`)
+- Add webpack configuration files
+- Update package.json with webpack dependencies
+- Keep both build systems working
+**Why:** Allows testing without breaking existing setup
+
+#### PR #2: Prepare for React on Rails
+**Branch:** `prepare-react-on-rails-structure`
+**Changes:**
+- Reorganize `app/frontend` → `app/javascript` (symlink for compatibility)
+- Add bundles directory structure
+- Update import paths to be flexible
+- Add `.babelrc` and webpack configs
+**Why:** Sets up structure without breaking Inertia
+
+#### PR #3: Add React on Rails gem
+**Branch:** `add-react-on-rails-gem`
+**Changes:**
+- Add `react_on_rails` gem
+- Add initializer (disabled by default)
+- Add helper methods to ApplicationController
+- Documentation for enabling
+**Why:** Makes gem available without forcing usage
+
+### Phase 2: Parallel Implementation PRs
+
+#### PR #4: Dual-mode components
+**Branch:** `dual-mode-components`
+**Changes:**
+- Create React on Rails versions of components
+- Add registration scripts
+- Keep Inertia components unchanged
+- Add environment variable to switch modes
+**Why:** Allows A/B testing both approaches
+
+#### PR #5: View templates
+**Branch:** `add-view-templates`
+**Changes:**
+- Create `.html.erb` files for each route
+- Use conditional rendering (Inertia vs React on Rails)
+- Add layout files
+- Keep controllers unchanged
+**Why:** Prepares view layer without breaking Inertia
+
+#### PR #6: SSR implementation
+**Branch:** `implement-ssr`
+**Changes:**
+- Add server bundle configuration
+- Configure SSR for React on Rails
+- Add prerender options
+- Performance benchmarks
+**Why:** Shows SSR benefits
+
+### Phase 3: Migration Tooling PRs
+
+#### PR #7: Migration script
+**Branch:** `add-migration-script`
+**Changes:**
+```ruby
+# lib/tasks/migrate_to_react_on_rails.rake
+namespace :react_on_rails do
+  desc "Migrate from Inertia to React on Rails"
+  task :migrate => :environment do
+    # Automated migration tasks
+  end
+end
+```
+**Why:** Helps users migrate easily
+
+#### PR #8: Feature flags
+**Branch:** `add-feature-flags`
+**Changes:**
+- Add config flags to switch between Inertia/React on Rails
+- Environment-based configuration
+- Documentation
+**Why:** Allows gradual rollout
+
+### Phase 4: Optimization PRs
+
+#### PR #9: Replace Vite with Shakapacker
+**Branch:** `shakapacker-primary`
+**Changes:**
+- Make Shakapacker the default
+- Move Vite to optional
+- Update development scripts
+- Update deployment configs
+**Why:** Better Rails integration
+
+#### PR #10: Performance optimizations
+**Branch:** `performance-optimizations`
+**Changes:**
+- Code splitting configuration
+- Caching strategies
+- Bundle optimization
+- CDN setup
+**Why:** Production readiness
+
+### Phase 5: Future RSC Preparation
+
+#### PR #11: RSC-ready architecture
+**Branch:** `rsc-preparation`
+**Changes:**
+- Add 'use client' directives where appropriate
+- Separate server/client components
+- Document RSC upgrade path
+- Add Pro version detection
+**Why:** Future-proofing
+
+## File Structure Evolution
+
+```
+react-starter-kit/
+├── app/
+│   ├── frontend/          # Original (Phase 1)
+│   ├── javascript/        # New (Phase 2+)
+│   │   ├── bundles/       # React on Rails components
+│   │   ├── packs/         # Entry points
+│   │   └── components/    # Shared components
+│   └── views/
+│       └── [controllers]/ # New view templates
+├── config/
+│   ├── inertia_rails.rb  # Keep
+│   ├── react_on_rails.rb # Add
+│   ├── shakapacker.yml    # Add
+│   └── vite.json          # Keep initially
+└── package.json           # Both dependencies
+```
+
+## PR Guidelines
+
+### Each PR Should:
+1. **Be focused**: One feature/change per PR
+2. **Be backward compatible**: Don't break existing functionality
+3. **Include tests**: Add specs for new features
+4. **Have documentation**: Update README with migration notes
+5. **Show benchmarks**: Performance comparisons where relevant
+
+### Commit Message Format
+```
+feat(shakapacker): Add Shakapacker alongside Vite
+
+- Add shakapacker gem to Gemfile
+- Configure webpack for development/production
+- Update bin scripts for dual-mode operation
+- Keep Vite as default, Shakapacker as opt-in
+
+BREAKING CHANGE: None
+Migration: Set USE_SHAKAPACKER=true to test
+```
+
+## Timeline Estimate
+
+| Phase | PRs | Time | Notes |
+|-------|-----|------|-------|
+| Phase 1 | PR 1-3 | Week 1 | Foundation, non-breaking |
+| Phase 2 | PR 4-6 | Week 2 | Parallel implementation |
+| Phase 3 | PR 7-8 | Week 3 | Migration tooling |
+| Phase 4 | PR 9-10 | Week 4 | Optimization |
+| Phase 5 | PR 11 | Week 5 | Future preparation |
+
+## Benefits of This Approach
+
+1. **Non-breaking**: Users can adopt gradually
+2. **Testable**: Each PR can be tested independently
+3. **Reversible**: Can roll back if issues arise
+4. **Educational**: Community learns by following PRs
+5. **Collaborative**: Others can contribute to specific PRs
+
+## Quick Start Commands
+
+```bash
+# Fork and setup
+gh repo fork inertia-rails/react-starter-kit --clone
+cd react-starter-kit
+
+# Create first PR branch
+git checkout -b add-shakapacker-support
+
+# Install dependencies
+bundle add shakapacker --group "development, production"
+bundle install
+
+# Generate Shakapacker config
+bundle exec rails shakapacker:install
+
+# Create PR
+gh pr create --title "Add Shakapacker support alongside Vite" \
+  --body "First step in migration to React on Rails"
+```
+
+## Communication Strategy
+
+### PR Description Template
+```markdown
+## What does this PR do?
+[Describe the changes]
+
+## Why is this change needed?
+[Explain the benefits]
+
+## How to test?
+1. [Step by step instructions]
+2. [Expected results]
+
+## Migration impact
+- [ ] Breaking change
+- [ ] Requires migration
+- [ ] Documentation updated
+
+## Performance
+| Metric | Before | After |
+|--------|--------|-------|
+| Build time | X | Y |
+
+## Related issues
+Refs #[issue number]
+```
+
+## Next Steps
+
+1. **Fork the repository** (outside demos folder)
+2. **Create first PR** (Shakapacker support)
+3. **Open discussion issue** explaining migration plan
+4. **Engage community** for feedback
+5. **Iterate based on feedback**
+
+This incremental approach ensures:
+- Community buy-in
+- Gradual adoption
+- Learning opportunity
+- Maintained stability
+- Clear upgrade path to Pro features later