fix(libkernel): keep ymm upper halves across a redirected raise

A thread that sceKernelRaiseException redirects resumes through
RtlRestoreContext with a CONTEXT that has no XSTATE, so the upper halves
of ymm0-ymm15 came back as the handler and the delivery path left them.
A handler or host routine that runs vzeroupper or any VEX instruction
(Zen 2 guest code, the CRT's memcpy) cleared the upper lanes of a thread
interrupted in the middle of AVX code. The entry stub now stores
ymm0-ymm15 next to the delivery when the CPU and the OS enable AVX, and
the exit loads them back right before RtlRestoreContext, which restores
only the low halves.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01HeC9bA3n74TzJRYv9AgBE8

docs/dev/TechnicalDebt.md

@@ -237,7 +237,6 @@ Throughout the project, every function at every stage either **does exactly what
 - [sceKernelRaiseException](../../core/libs/prx/libkernel/System/src/Exception.cpp) delivers on Windows only and throws on Linux
 - [sceKernelRaiseException](../../core/libs/prx/libkernel/System/src/Exception.cpp) builds the handler's `ucontext` with FreeBSD's amd64 layout (16-byte sigmask, `mcontext` at 0x40, `mc_rsp` at 0xf8); the console's layout is not verified beyond the fields PS5Util reads
 - [sceKernelRaiseException](../../core/libs/prx/libkernel/System/src/Exception.cpp) does not consult the target thread's signal mask
-- [sceKernelRaiseException](../../core/libs/prx/libkernel/System/src/Exception.cpp) saves and restores only `CONTEXT_FULL | CONTEXT_FLOATING_POINT` on Windows, so the upper halves of the YMM registers are not preserved if the handler or the entry uses AVX
 - [sceKernelRaiseException](../../core/libs/prx/libkernel/System/src/Exception.cpp) reaches a thread that waits in an alertable `TimedWait` wait through an APC. A thread blocked anywhere else, including all waits under `APS5_COARSE_TIMED_WAITS` and host waits inside the emulator, is redirected and runs the handler only when that wait returns
 - [libSceUlt queues](../../core/libs/prx/libSceUlt/Export.cpp) use preallocated host storage instead of the supplied guest work area; its existing size formula and the 512-byte object layouts remain unverified. Waiting-queue pool thread limits and waiter priority ordering are not implemented. Finalization wakes blocked queue callers with `ULT_ERROR_STATE`.
 - [Thread cancellation](../../core/libs/prx/libkernel/Pthread/src/Thread.cpp) (libkernel) is not modelled: `scePthreadCancel` throws, so no cancel request is ever pending and `scePthreadTestcancel` and `pthread_testcancel` return without acting; the cancel state and type set by `scePthreadSetcancelstate` and `scePthreadSetcanceltype` are stored and not used