fix: make BT A2DP output exclusive to one process

The A2DP output is a single unmixed PCM stream. A second process
opening audio while a stream was active would reconfigure the SBC
encoder and media clock under the owner and interleave both apps' PCM
into one ring, garbling playback (e.g. launching DOOM destabilized
Music). Add ClaimOutput/ReleaseOutput pid ownership: the first opener
gets the BT sink, later openers fall back to the HDA mixer, and only
the owner can tear the stream down. The scheduler releases ownership
on process exit so a killed app cannot leak the claim.

Co-Authored-By: Claude Fable 5 <[email protected]>

kernel/src/Api/BuildNo.hpp

@@ -12,4 +12,4 @@
 
 #pragma once
 
-#define MONTAUK_BUILD_NUMBER 3
+#define MONTAUK_BUILD_NUMBER 4