Complete toolchain implementation and add comprehensive testing

[avrabe]

Description

This issue tracks the work needed to complete the rules_rocq_rust implementation:

Remaining Work

1. Toolchain Implementation

   • Complete binary download and verification
   • Add platform-specific toolchain support
   • Implement hermetic toolchain management

2. coq-of-rust Integration

   • Finish OCaml toolchain implementation
   • Enable coq-of-rust extensions
   • Add Rust to Coq translation support

3. Testing Infrastructure

   • Create comprehensive test suite
   • Set up CI/CD pipeline
   • Add mock toolchain for testing
   • Implement integration tests

4. Documentation

   • Complete API reference
   • Add contribution guide
   • Create advanced examples

Acceptance Criteria

• All toolchain features working
• coq-of-rust integration complete
• CI/CD pipeline set up and passing
• Comprehensive test coverage
• Complete documentation

Related

• Fixes Complete toolchain implementation and add comprehensive testing #1 (initial implementation)
• Part of rules_rocq_rust roadmap

Priority

High - These features are needed for production use