Archives #38, #39, #40 with full learnings, per the document-as-you-go discipline.

The thread: the onboard SOF codec stopped answering IPC mid-session and took the
whole audio stack down with it — WirePlumber wedged in uninterruptible D-state
inside ipc3_tx_msg_unlocked, unkillable by SIGKILL, scsynth dead, reboot the only
exit. That escalated the UMC202HD from "nice upgrade" to "resilience fix", and the
move onto it is now done: default sink switched, the SOF internal DMIC (card3
pcm4c, the exact PCM that hung) disabled by a scoped WirePlumber rule that leaves
all five SOF playback sinks alone.

The archive's real value is the pattern that runs through all three entries. Every
failure this session had the same shape: a binding resolved once at startup,
invalidated by a device event, failing with NO error surfaced. Ardour's master port
(twice — it restores its own saved ports and ignores the default sink, then loses
the link entirely on a wireplumber restart). SuperCollider's cached MIDIOut after a
replug moved the LCXL 20:0 -> 24:0. The HUD's aseqdump, still ALIVE on the dead
port, which is why its respawn-on-death recovery never fired — liveness is not
health. And the session layer itself: after an overnight suspend the UMC
re-enumerated 118 times, came back healthy at the hardware level, and WirePlumber
simply never rebuilt its node.

Also recorded: a wireplumber restart resets sink volume to the device default (87%),
which turned a routine verification tone into a painfully loud one. Attenuate before
making sound, always.

Corrected doctrine while here — commits belong on master by default. PLN is a lone
dev who reviews his own work; branches are for cloud agents, parallel sessions and
genuine prototypes. The memory claiming otherwise was wrong and cost real time.