Add autodiff-optimized sampling wrapper for automatic differentiation support (Proposal Type - Dev)

[ChinmayRout9040895625]

Summary

This PR adds a convenient wrapper for autodiff-enabled sampling in the volesti C++ library, providing template functions optimized for automatic differentiation workflows.

Changes

• New File: include/sampling/sampling_autodiff.hpp
  • Wrapper templates for autodiff-enabled sampling
  • Integrates with existing AutoDiffFunctor from oracle_autodiff_functors.hpp
  • Provides convenient interface for R bindings (Rvolesti)

The volesti library already has full autodiff support through AutoDiffFunctor and autopoint<T>.
This wrapper provides a clean interface for higher-level bindings (e.g., R interface via Rcpp)
that want to use automatic differentiation for sampling.

Technical Details

• Includes sampling.hpp for base sampling functionality
• Includes ode_solvers/oracle_autodiff_functors.hpp for autodiff functors
• Uses existing C++17 infrastructure
• Backward compatible - no existing code affected

Testing

• Builds without warnings
• Compatible with existing test suite
• No new tests needed (convenience wrapper only)

Dependencies

• C++17 (already required by volesti)
• Existing Autodiff library (already in external/

Enables GSOC 2026 project: "Expose autodiff to R interface of volesti"

Checklist

• Code builds without errors
• No compiler warnings
• Backward compatible
• Follows volesti code style
• Headers properly guarded