sceKernelInstallExceptionHandler and sceKernelRemoveExceptionHandler threw.
They now keep one handler per allowed signal (SIGHUP, SIGILL, SIGFPE,
SIGBUS, SIGSEGV, SIGUSR1, as in shadPS4): another signal or a null handler
returns EINVAL, a second handler for a signal returns EAGAIN, and removing
clears it. Delivery is not implemented and is recorded in the technical
debt; sceKernelRaiseException still throws.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>