Add per-laptop speaker tunings, starting with the XPS 14

Laptop speakers ship voiced by the vendor's Windows DSP layer, which Linux does
not get. A tuning restores that as a PipeWire filter-chain in front of the
internal speaker sink, matched to the machine by DMI string and expected sink.

Adding a laptop is a directory under default/audio/tunings with two files and no
new code: matching is data. The XPS 14 DA14260 tuning included here was derived by
measuring the xps-audio-linux EasyEffects profile (MIT) and fitting a biquad chain
to it, so no impulse response or other upstream asset is redistributed. It measures
1.24 dB RMS against that reference, and matches its dynamic range within 0.1 LU --
the reference's multiband compressor turned out to contribute nothing, so a linear
chain replaces it. Bass Q is capped deliberately: a closer magnitude fit swung
group delay 31 ms across 63-80 Hz, which smears bass transients.

The graph runs as its own PipeWire client under its own config name rather than
loading into the audio daemon. The daemon only reads its config at startup, so a
daemon-loaded tuning could only be switched by restarting PipeWire -- which drops
every PulseAudio client's connection, and applications that do not reconnect
(Spotify) then have to be restarted by hand. Hosting it separately also contains
failure, since a malformed tuning breaks only that service.

Three things about the surrounding audio graph needed fixing for this to behave:

- Volume must live downstream of the tuning. omarchy-audio-output-sink is now the
  single definition of which sink an output's volume really uses, shared by the
  volume keys, the output switcher's OSD and the audio panel, so they cannot
  disagree. It resolves the current default output, which keeps it correct when
  headphones are selected while a tuning exists.
- The tuning's own output is a movable sink input, so rerouting "all streams" to a
  newly selected output would drag the processing onto headphones, or into the
  tuning's own sink, which is a cycle. It is pinned, and stream moves are limited
  to streams carrying an application.name.
- The physical sink a tuning fronts is not independently selectable, since picking
  it would only bypass the tuning, so it is kept out of the output list.

Applying happens at first-run, not finalize-user, because finalize-user also runs
in the ISO chroot where there is no audio server and nothing would retry.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

migrations/1784960000.sh

@@ -0,0 +1,10 @@
+echo "Install the speaker tuning for this laptop, if one ships for it"
+
+# Speaker tunings are PipeWire filter-chain drop-ins gated on a hardware
+# predicate, so this is a no-op on machines without one. The limiter is an LV2
+# plugin and the graph will not instantiate without it.
+
+if omarchy-audio-tuning match >/dev/null 2>&1; then
+  omarchy-pkg-add lsp-plugins-lv2
+  omarchy-audio-tuning on
+fi