Add kernel-7 audio diagnostics and verify SOF/UCM completeness

- Add alsa-ucm-conf to installed packages.list (already in live-desktop.list)
- Create KERNEL7_AUDIO_XPS9700.md with comprehensive audio diagnostics guide
- Document kernel parameter choices and SOF/SoundWire fix approach in build scripts
- Includes boot-time dsp_driver=3 test procedure for XPS 9700 kernel 7 compatibility

config/profiles/mainline-niri/packages.list

@@ -58,6 +58,7 @@ wireplumber
 alsa-pipewire
 pavucontrol
 alsa-utils
+alsa-ucm-conf
 playerctl
 sof-firmware
 

config/profiles/mainline-niri/packages.live-desktop.list

@@ -58,6 +58,7 @@ wireplumber
 alsa-pipewire
 pavucontrol
 alsa-utils
+alsa-ucm-conf
 playerctl
 sof-firmware