[MAINTENANCE] Rename TrafficLayer to FIXS_Core and reorganize repository structure

[yunlishao]

Task Summary

1. Rename TrafficLayer.exe to FIXS_Core.exe (or FIXS.exe)
2. Reorganize repository with proper src/ directory structure
3. Improve overall file organization and folder hierarchy

Why is this needed?

• TrafficLayer.exe is the core executable of the FIXS framework but the name doesn't reflect this
• Current flat repository structure makes it difficult to navigate and understand the project layout
• Better organization will improve maintainability and onboarding for new developers
• Industry standard practice is to have src/, include/, tests/, docs/ structure

Scope of Work
Components involved:

• TrafficLayer/ directory → rename to FIXS_Core/ or restructure
• TrafficLayer.exe output name → FIXS_Core.exe or FIXS.exe
• Update all build scripts, documentation, and references
• Reorganize repository structure:
  • Consider src/ for source code
  • include/ or CommonLib/ for headers
  • tests/ already exists but may need reorganization
  • scripts/ for build and utility scripts
  • docs/ for documentation

Proposed Structure (to be finalized)

FIXS/
├── src/
│   ├── FIXS_Core/        (formerly TrafficLayer)
│   ├── ControlLayer/
│   ├── VehicleClient/
│   └── ...
├── include/              (formerly CommonLib headers?)
├── lib/                  (third-party libraries)
├── tests/
├── scripts/
├── docs/
└── README.md

Risks or Dependencies

• Requires updating all build configurations (Visual Studio projects, CMake if applicable)
• Documentation updates needed across README, setup guides, examples
• May break existing user scripts or workflows that reference TrafficLayer.exe
• Should coordinate with any ongoing PRs to minimize merge conflicts

Additional Context

• Related to clean up #7 (cleanup task)
• Should be done after version management system is in place (handled in separate PR)
• Consider creating a migration guide for users
• May want to keep symbolic link or alias for backward compatibility during transition period