docs: audio boot-profile regression and fix

kernel r162 routed capture strictly mono 48k; undeclared UCM Mic
probe failed, no profiles formed at boot, card fell to pro-audio.
CaptureChannels/CaptureRate in both Mic devices restores the probe;
probe mechanics recorded for the next time.

PAF/audio.md

@@ -31,6 +31,57 @@ name `souveraine-callaudio`), `pkgs/souveraine-callaudiod`, and
 Everything below is the evidence ledger. Headings such as “still open” describe
 the date beneath them unless the current block above repeats the defect.
 
+## UCM PROFILE GONE AT BOOT — 2026-08-16, fixed same day
+
+Boot-time music died after kernel `7.1.1.r162.g457a667bd3eb` (installed
+2026-08-13, first boot 08-16 00:46): the card came up with only `off` and
+`pro-audio`, no UCM profiles, so no HiFi sink existed at boot. In-session
+audio (calls, STT mic) kept working — the regression only hit the fresh-boot
+state, which is why it surfaced as “music at boot”.
+
+Measured chain, all on-device:
+
+- **Kernel made routed capture strictly mono 48k.** The wcd934x
+  recorder-state work in r162 (`b30e849be` “program all DMIC interface pads”,
+  `9610ef9cf` “replay complete blueline recorder state”) rejects stereo
+  capture hw_params on the routed MultiMedia2 (`CHANNELS: [1 4]` advertised,
+  but `arecord -c 2` → -EINVAL, `-c 1` → fine).
+- **ACP probes with declared UCM values.** The Mic devices declared no
+  `CaptureChannels`/`CaptureRate`, so ACP assumed stereo at the FE-default
+  rate → capture probe failed -EINVAL → every profile “not supported” → ACP
+  fell back to `pro-audio` (priority 1) at boot.
+- **Secondary lock, not the cause:** `90-blueline.conf` sets
+  `session.suspend-timeout-seconds = 0` on `~alsa_output.*`, so the pro-audio
+  sink never released hw:0,0; later probes died “Device or resource busy”.
+  The persisted `default-profile` state (wireplumber saves the selected
+  profile, by design) then re-pinned `pro-audio` each boot.
+- **Fix:** declared `CaptureChannels 1` + `CaptureRate 48000` in both Mic
+  devices (HiFi + VoiceCall). ACP probe now succeeds; all three UCM profiles
+  form; card activates HiFi at boot. Tone verified audible on glass; mic
+  capture nonzero through the UCM source. Shipped as
+  `souveraine-ucm-blueline 0.1.0-2` (commit `9f0f103`, CI run 1696);
+  rootfs-overlay UCM copies kept identical to the package.
+- **Not shipped, known hardening:** scope the never-suspend output rule to
+  `~alsa_output.platform-sound.*__sink` (the UCM sinks) so a stray pro-audio
+  fallback can never hold hw:0,0 forever.
+
+Probe mechanics learned (canonical, 2026-08-16):
+
+- `spa-acp-tool -v -v hw:0` is the ACP probe; “Probing profile X” with no
+  failure lines after it = supported. The trailing “unknown command hw:0” is
+  a harmless arg-parsing quirk.
+- `alsaucm -c hw:0 set _verb HiFi` is the real-card UCM branch; it runs the
+  verb EnableSequence (and enables devices — TX5 mapping included). `-c G3`
+  and `-c "Google Pixel 3"` hit the *no-hw* branch (conf.virt.d / legacy
+  paths) and fail ENOENT even when UCM is healthy — red herrings.
+- `alsaucm list profiles` / `get _verbs` fail with ENOENT quirks on this
+  box; they are not valid probes.
+- `cat /proc/asound/card0/pcm*p/sub0/status` shows `owner_pid` — the way to
+  find who holds a PCM.
+- Raw `arecord -D hw:0,1` only works while the verb routes are applied;
+  `spa-acp-tool` runs DisableSequence on exit and tears them. Re-apply the
+  verb before raw capture tests.
+
 ## PIPEWIRE RESTORED — 2026-07-19 late evening
 
 The PA-native arrangement is retired. Live state, all verified on-device:

STATE.md

@@ -18,8 +18,19 @@ stale the same way for the same reason. The packages are now cured
 archive, so `pacman -Sl souveraine-aarch64` is the manifest. The surface gap
 (a souveraine overlay host for the subconscious views) is still open.
 
-Last updated: 2026-08-15 (the charge lane and the machined handoff; see
-below).
+Last updated: 2026-08-16 (audio: boot-time UCM profiles restored; see
+below and `PAF/audio.md`).
+
+## 2026-08-16 — boot-time audio regression fixed
+
+Kernel r162 (`g457a667bd3eb`, installed 08-13, first boot 08-16) made the
+routed MultiMedia2 capture strictly mono 48k; the UCM Mic devices declared
+no channels/rate, so ACP's probe failed -EINVAL, no UCM profile formed, and
+the card booted into `pro-audio` (no HiFi sink → boot-time music dead).
+Declared `CaptureChannels 1` + `CaptureRate 48000` in both Mic devices;
+profiles probe clean and HiFi activates at boot again. Shipped as
+`souveraine-ucm-blueline 0.1.0-2` (Pixel3Arch commit `9f0f103`); full chain
+and probe mechanics in `PAF/audio.md`.
 
 ## 2026-08-15 — charge becomes a sensor source; machined is handed over