D417 - Three more HLE fixes from the same diff: thread join, mutex type, audio init

measured - 2026-08-31

Continuing D416 down the hardware-vs-orbistoun divergence list, each confirmed by the verdict flipping when obSCEne re-runs:

• scePthreadJoin carries the thread's return value back (orbistoun-kernel, orbistoun-kernel/thread). enter_guest_with_argument already returns the guest thread function's rax; spawn now keeps it in an exit-value map and join makes it available once the host thread ends, so scePthreadJoin writes the real value through its out-parameter instead of a zero. 030-thread/join partial -> pass.
• Mutex type is honoured (orbistoun-kernel/sync). pthread_mutex_init ignored the attribute's type and every lock was non-recursive, so a self-trylock always answered busy. It now reads the type the attribute already stored (ATTR_TYPE): 2 is recursive, 4 is error-checking. try_lock grew a third outcome - the owner re-taking a recursive lock is locked, a normal one is busy, an error-checking one is a deadlock - which scePthreadMutexTrylock maps to 0x0 / 0x8002_0010 / 0x8002_0016, matching the console's three answers in 015-sync/mutex-recursion.
• sceAudioOutInit succeeds (orbistoun-audio). The crate declared the audio surface but exposed no implementations, so every call including init fell to the placeholder's non-zero code and 090-audio/initialise read a failed init. Init now answers success - the port calls that would move samples stay unimplemented, because there is no backend and pretending is the D171 shape.

sceKernelCreateSema (018-relational/handle-fits) was on the list and deliberately left alone: its verdict differs because hardware fails it - the console writes past the end of the int - while orbistoun writes a clean four-byte handle. orbistoun is the more correct of the two, and matching the quirk would mean writing a bug.

Total across D416+D417 vs the pre-fix run: 516 -> 522 pass, 12 -> 8 partial, 8 -> 6 skip, fails unchanged, plus the LoadStartModule and mutex measures now matching hardware. Recorded measured.