feat(compiler): add native LLVM object emission (#242)

* feat(compiler): add native LLVM object emission

- ship the pinned macOS arm64 LLVM helper and platform package
- add assembly/object CLI outputs, caching, diagnostics, and runtime ABI checks
- validate helper artifacts through CI, packaging, docs, and differential coverage

* fix(compiler): harden native LLVM emission

* fix(compiler): harden LLVM helper packaging

* fix(compiler): stabilize LLVM helper package size

* fix(compiler): harden native helper validation

* fix(compiler): harden LLVM helper verification

* fix(compiler): harden native object emission