[CORE] Invert object/type_traits dependency layering

[tqchen]

Summary

• invert the header dependency so object.h includes type_traits.h, and move shared type metadata/helpers like StaticTypeKey, TypeIndexToTypeKey, and details::type_contains_v into type_traits.h
• move object and Optional trait specializations into their owning headers, move DLTensor* traits into tensor.h, and keep the uint64_t overflow-checked specialization near the end of any.h
• add a narrow ASF header checker skip for .agents/skills/**/SKILL.md so skill files can keep frontmatter at byte 0

[gemini-code-assist]

Code Review

This pull request refactors the TVM FFI type traits and error-handling mechanisms to break circular dependencies and improve header organization. It introduces a low-level error_throw.h header, moves core type traits and static type keys to type_traits.h, and extracts object-dependent traits into a new object_type_traits.h header. Additionally, a TypeTraits specialization for Optional has been added. The feedback suggests explicitly including <tvm/ffi/object.h> in <tvm/ffi/object_type_traits.h> to ensure header self-containment and prevent compilation failures when it is included directly.

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