The System/JACK (CpalDefaultBackend) and output_sinks enumerations dumped
CPAL's raw ALSA PCM list: the `null` discard sink plus one output repeated
across every plugin profile (8x/Nx duplicates that share a display name).
The precise pickers (ALSA /proc/asound, PipeWire pactl) were already clean;
only these CPAL paths lacked filtering.
Add device_filter::retain_real_outputs(): collapses entries that share a
display name (keeping the best-ranked id), and sorts the `null` discard
sink to the end instead of offering it as a first-class output. Pure,
host-agnostic (PipeWire node names pass through), unit-tested.
cc
vicrodh
c75a0af5b2