Pre-reset exploratory run (2026-09-21, guest 6.5-DEVELOPMENT): after
kldload snd_cs4281 (module loads, registers pci/snd_cs4281, probes no
device) a kldunload wedged the guest in DDB:

  panic: sbuf_delete called with uninitialized or corrupt sbuf
  cpuid = 4
  _assert_sbuf_integrity() at _assert_sbuf_integrity+0x42
  sbuf_delete() at sbuf_delete+0x1b
  sndstat_sysuninit() at sndstat_sysuninit+0x8c
  linker_file_unload() at linker_file_unload+0x3aa

Root cause is the sound core, already filed as DF-4116 ("Guaranteed
kernel panic in sndstat_sysuninit on sound.ko unload"). It is NOT a
cs4281.c defect; recorded here because it aborted the first probe
session and forced `vm.sh reset with-src`. The final run.log comes from
the clean post-reset guest with no module loads.