The fallback CONTEXT definition at lines 2073-2124 was unreachable dead code.
The guard '#if defined(__aarch64__) && !defined(_ARM64_CONTEXT_DECLARED)'
could never be true because:
1. Line 50-51: __aarch64__ automatically defines _ARM64_
2. Line 1426: #if defined(_ARM64_) || defined(__aarch64__) always enters
3. Line 1473: _ARM64_CONTEXT_DECLARED is always defined inside that block
4. Line 2073: The fallback guard is therefore always false
This 52-line duplicate was a maintenance hazard that could silently diverge
from the official ARM64_NT_CONTEXT definition. Remove it entirely.
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