pub fn join_task(wait_tid: u32) -> Result<(u32, i32), SyscallError>Expand description
Core of SYS_THREAD_JOIN and /thread/join/<tid>.
Blocking reap loop: only children of the calling task can be joined,
self-join is EINVAL, absent or already-reaped targets yield ENOENT.
Returns (tid, exit_code).