Organize Risch method into dedicated folder structure

[ChrisRackauckas-Claude]

📁 Organize Risch Method into Dedicated Folder Structure

This PR organizes all Risch algorithm components into a clean, dedicated folder structure for better maintainability and extensibility.

📁 New Folder Organization

Source Structure

src/
├── SymbolicIntegration.jl          # Main module
├── frontend.jl                     # Frontend interface
├── methods.jl                      # Method dispatch system
└── methods/risch/                  # Risch algorithm components
    ├── general.jl                  # General algorithms (Chapter 1)
    ├── rational_functions.jl       # Rational integration (Chapter 2)  
    ├── differential_fields.jl      # Differential field operations
    ├── complex_fields.jl           # Complex field handling
    ├── transcendental_functions.jl # Transcendental functions (Ch 5-6)
    ├── risch_diffeq.jl            # Risch differential equations
    ├── parametric_problems.jl      # Parametric integration problems
    ├── coupled_differential_systems.jl # Coupled differential systems
    └── algebraic_functions.jl      # Algebraic function handling

Test Structure

test/
├── runtests.jl                     # Main test runner
├── test_stewart_examples.jl        # General integration examples
└── methods/risch/                  # Risch-specific tests
    ├── test_rational_integration.jl    # Rational function tests
    ├── test_complex_fields.jl          # Complex field tests
    ├── test_bronstein_examples.jl      # Bronstein book examples
    ├── test_algorithm_internals.jl     # Internal algorithm tests
    ├── bronstein_examples.jl           # Original Bronstein examples
    └── test_integrate_rational.jl      # Original rational tests

🔧 Pure File Reorganization

What Changed

• Moved 9 Risch algorithm files to src/methods/risch/
• Moved 6 Risch test files to test/methods/risch/
• Updated include paths in main module and tests
• Clean folder separation by algorithm method

What Stayed The Same

• ✅ All functionality preserved - same algorithms, same results
• ✅ No code changes - pure file movement
• ✅ All tests pass - no behavioral changes
• ✅ Same API - integrate() function unchanged

✅ Verified Functionality

All integration capabilities maintained:

• ✅ 102 tests passing (unchanged)
• ✅ 1 test broken (documented)
• ✅ 0 tests errored
• ✅ Method dispatch: integrate(f, x, RischMethod())
• ✅ Complex root integration: ∫1/(x²+1) = atan(x)
• ✅ All Bronstein algorithms working

🎯 Benefits

Organization

• Clear method separation: All Risch components in one folder
• Logical grouping: Tests organized by method
• Extensible structure: Ready for additional integration methods
• Professional layout: Clean, maintainable architecture

Future Development

• Easy to add new methods: Just create new method folders
• Clear algorithm boundaries: Each method self-contained
• Simplified maintenance: Method-specific file organization
• Community contributions: Clear structure for new algorithms

🔗 Ecosystem Readiness

This organization pattern:

• Follows SciML standards: Method-based folder organization
• Supports multiple algorithms: Framework for various integration methods
• Professional structure: Ready for JuliaSymbolics ecosystem
• Maintainable codebase: Clear separation of concerns

Perfect foundation for a multi-method symbolic integration package! 📁🚀

🤖 Generated with Claude Code