A non-faulting probe payload returns (rsp+8)&15 from the callee, which is 0
only when the stub delivers callee entry rsp ≡ 8 (mod 16) per the Microsoft
x64 ABI. Proves the stub frame alignment end-to-end through CreateRemoteThread
without risking a #GP that would crash the in-process test host. Verified to
fail against the old fixed-0x20 frame.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>