fix: Add missing yaml header

[gau-nernst]

Describe Your Changes

• Add missing yaml-cpp/yaml.h header to get definition for YAML::Node::IsDefined()

On my Windows VM, it fails to build without that header

model_source_service.obj : error LNK2019: unresolved external symbol "public: bool __cdecl YA
ML::Node::IsDefined(void)const " (?IsDefined@Node@YAML@@QEBA_NXZ) referenced in function "cla
ss std::optional<class std::basic_string<char,struct std::char_traits<char>,class std::alloca
tor<char> > > __cdecl huggingface_utils::GetModelAuthorCortexsoHub(class std::basic_string<ch
ar,struct std::char_traits<char>,class std::allocator<char> > const &)" (?GetModelAuthorCorte
xsoHub@huggingface_utils@@YA?AV?$optional@V?$basic_string@DU?$char_traits@D@std@@V?$allocator
@D@2@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@3@@Z) [C:\Users\
menlo\cortex.cpp\engine\build\cortex-server.vcxproj]
C:\Users\menlo\cortex.cpp\engine\build\cortex-server.exe : fatal error LNK1120: 1 unresolved
externals [C:\Users\menlo\cortex.cpp\engine\build\cortex-server.vcxproj]

Fixes Issues

• Closes #
• Closes #

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed