docs(libSceAjm): say the empty PS4 batch contract needs a non-null address

A null batch address is refused whatever the size, so the accepted batch
of zero bytes is one at a real address, which is what TestConsoleEmptyBatch
starts.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/dev/debt/libSceAjm.native.md

@@ -20,7 +20,7 @@
 - [sceAjmBatchJobControlBufferRa, sceAjmBatchJobRunBufferRa, sceAjmBatchJobRunSplitBufferRa, sceAjmBatchStartBuffer](../../../core/libs/prx/libSceAjm.native/src/Ajm.cpp) (libSceAjm, PS4) - the batch layout (chunk kinds, 20-bit payload, flags bits 32-51 as the flags chunk's payload, the builders' chunk order) follows [shadPS4](https://github.com/shadps4-emu/shadPS4/blob/854b291c63360ff24e590809aff54cf5ab2dd4c9/src/core/libraries/ajm/ajm_batch.cpp) and was confirmed byte for byte for 64-byte control and 80-byte run jobs by a PS4 trace of Knowledge is Power: Decades (CUSA12435, Wwise, 32 545 batches dumped by a GoldHEN plugin). The console's builders write only bits 0-3 (kind), bit 4 (a buffer chunk's output direction) and bits 6-25 (payload) of the header word and leave bits 5, 26, 27 and 31 as the previous batch left them, so the kind is read as 4 bits plus the direction bit, not as 6 bits
 - [sceAjmBatchStartBuffer](../../../core/libs/prx/libSceAjm.native/src/Ajm.cpp) (libSceAjm, PS4) - the statistics instance 0x80000 and the inline chunk come from shadPS4 only: the traced title builds every batch with the builders and a return address, and no title was seen writing an inline chunk. Flags are kept as passed. Unknown chunk kinds, control flags other than RESET, INITIALIZE and SIDEBAND_GAPLESS_DECODE, control jobs with run buffers and run jobs with a control input throw
 - [sceAjmBatchStartBuffer refusals](../../../core/libs/prx/libSceAjm.native/src/Ajm.cpp) (libSceAjm, PS4) - probe batches through the console's builders on a PS4 showed that a run buffer chunk of size zero is dropped whatever its address (the job runs as without it: 0x10 and nothing consumed for no room, 0 for no input), and that a null address with a nonzero size refuses the batch before any of its jobs runs, with 0x80930011 returned and the error record holding 0x80930016, the job chunk's address, the chunk's offset in the job and the job's return address. Control buffer chunks follow the same rule here, not measured. A size not a multiple of 8, a chunk that overruns its job or the batch, or a job without flags are refused the same way with 0x80930011 in the record; the console's report for those was not measured
-- [sceAjmBatchStartBuffer null and empty batches](../../../core/libs/prx/libSceAjm.native/src/Ajm.cpp) (libSceAjm, PS4) - a null batch address returns 0x80930005 whatever the size, as the PS5 builders' sceAjmBatchInitialize does for a null buffer, and a batch of zero bytes is accepted, runs nothing and completes at once; neither was measured on a console (the probe that passed a null batch froze the console before a result was written, so it is not retried on hardware)
+- [sceAjmBatchStartBuffer null and empty batches](../../../core/libs/prx/libSceAjm.native/src/Ajm.cpp) (libSceAjm, PS4) - a null batch address returns 0x80930005 whatever the size, as the PS5 builders' sceAjmBatchInitialize does for a null buffer, and a batch of zero bytes at a non-null address is accepted, runs nothing and completes at once (a null address with size 0 is refused like any null address); neither was measured on a console (the probe that passed a null batch froze the console before a result was written, so it is not retried on hardware)
 - [ATRAC9 run results](../../../core/libs/prx/libSceAjm.native/src/Ajm.cpp) (libSceAjm.native) - probe runs of a title's ATRAC9 stream through the console's builders on a PS4 showed the run result naming the side that ran out: `PARTIAL_INPUT` (0x8) when the input ran out with room left, on a superframe boundary or not; `NOT_ENOUGH_ROOM` (0x10) when the room ran out with input left, after any number of frames, and with nothing consumed for a zero room; both (0x18) when the input ended just as the output filled, which is every Wwise run job. ATRAC9 run jobs with `RUN_MULTIPLE_FRAMES` follow those rules here, vibration streams included, which were not traced; resampled runs and the other codecs keep the earlier rule (a trailing partial frame is partial input, a run that produced nothing is out of room)
 - [ATRAC9 run without RUN_MULTIPLE_FRAMES](../../../core/libs/prx/libSceAjm.native/src/Ajm.cpp) (libSceAjm.native) - the same PS4 probe decoded exactly one frame and reported 0 for such a run, and a job read from a PS4 batch buffer (sceAjmBatchStartBuffer) does the same here. A job from the PS5 builders still decodes its whole input, as FMOD in PPSA29141 needs (it puts two run jobs in one batch with the second's input right after the whole of the first's); whether a PS5 stops after one frame is not measured. MP3 and Opus run jobs stop after one frame on both paths. The console also rejected the tests' synthetic silent superframe after three frames (`CODEC_ERROR | FATAL`, internal result -577) where LibAtrac9 decodes four, so that vector proves job plumbing, not decoding; on the title's stream LibAtrac9 matched the console's PCM within 4 LSB, 83.5% of the samples exactly