Refactor projector_type enum to enum class for type safety and clarity

[wangqin0]

• Added explicit handling for ProjectorType::UNKNOWN for robustness. This should solve issue Llava functions compiled as extern "C" throw exceptions #7073.

It is still possible for clip_model_load to throw exceptions that will cause undefined behavior when reaching the C caller.

Test:

• GG_BUILD_CUDA=1 bash ./ci/run.sh ./tmp/results ./tmp/mnt returns 0 although no result output printed in console.

---

• I have read the contributing guidelines
• Self-reported review complexity:
  • Low
  • Medium
  • High

[slaren]

The changes to the projector_type enum are incompatible with the coding style of this project. Please revert these changes and remove only the exception.

[wangqin0]

Thanks for reviewing. I use enum class instead of enum because common, example and src have used enum class and it is more confined, type-safe, and part of C++11.