The fallback CONTEXT struct for ARM64 had multiple structural issues:
- ContextFlags was DWORD64 (8 bytes) instead of ULONG (4 bytes)
- Missing Cpsr field entirely
- Missing DECLSPEC_ALIGN(16) attribute
- X registers as simple array X[29] instead of union with named struct X[31]
These mismatches caused incorrect struct size and field offsets, leading to
register corruption when used with Windows APIs like GetThreadContext or
RtlRestoreContext.
The fallback struct now matches the official ARM64_NT_CONTEXT layout exactly,
ensuring binary compatibility with Windows ARM64 system calls.
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