Priorities outside the supported band and the calling process's own pid are unverified and are no longer pinned to throw. The worker test now sets a priority different from the caller's and checks both, so a no-op or a shared value fails.
sched_getparam, sched_getscheduler and sched_setparam are defined under libkernel/Pthread/Posix, so their typed declarations replace the no-argument placeholders in the libkernel header (public_headers requires the declaration in the implementing library's header), and GuestSchedParams.cpp includes the canonical headers instead of declaring these exports and the pthread, getpid and error calls locally.