serialization: scene save/load (Unity-style YAML + UE-style GUID registry)

Engine-layer SceneSerializer (yaml-cpp submodule): entities/components
to versioned YAML, atomic clear-and-rebuild on load with per-entity
fault tolerance, missing-field defaults, unknown-component skip and
UUID dedup. Asset references are {Guid, Path} pairs resolved through
the new AssetManager GUID registry (assets/asset_registry.yaml) with
path fallback; procedural:// pseudo-paths rebuild from parameters.
Editor File menu gets Save/Load Scene modals; app re-resolves stale
entity handles via onSceneLoaded callback.

CMakeLists.txt

@@ -59,6 +59,13 @@ set(ASSIMP_BUILD_STL_IMPORTER    ON CACHE BOOL "" FORCE)
 set(ASSIMP_BUILD_PLY_IMPORTER    ON CACHE BOOL "" FORCE)
 add_subdirectory(Lib/assimp)
 
+# ---- yaml-cpp（submodule，场景序列化；只编静态库本体）----
+set(YAML_CPP_BUILD_CONTRIB OFF CACHE BOOL "" FORCE)
+set(YAML_CPP_BUILD_TOOLS   OFF CACHE BOOL "" FORCE)
+set(YAML_CPP_BUILD_TESTS   OFF CACHE BOOL "" FORCE)
+set(YAML_CPP_INSTALL       OFF CACHE BOOL "" FORCE)
+add_subdirectory(Lib/yaml-cpp)
+
 
 
 # Vulkan