core_play_sound stored flags_and_slot (sound ID) in desc.flags_b instead
of priority (flags). This made all channels appear high-priority (IDs like
55, 121) so new sounds with real priority (1-8) could never evict them.
Channels accumulated until all 8 were permanently occupied, blocking all
subsequent pooled sounds (explosions, sizzle, etc.).
Also fixed stop_channel to unconditionally return pool entries to free list
even when the descriptor was already evicted by allocate_channel. WA does
this; without it, evicted pool entries leak and pool_free_count drops to 0.
Also fixed stop_channel used-list removal to use swap-remove (matching WA)
instead of shift-down.
Added sound_priority replay test.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
