Audacity 3.7.8 fails to "see" monitor ports on FreeBSD.

### Bug description

In plain old OSS mode, I have:

[1:31:331]root@hit:/usr/ports/audio/audacity> cat /dev/sndstat
Installed devices:
pcm0: (play/rec)
pcm1: (play) default
pcm2: (rec)
pcm3: (play)
pcm4: (play)
pcm5: (play)
pcm6: (play)
pcm7: (play/rec)
pcm8: (rec)
No devices installed from userspace.

Now... pcm1 (if read) will give back what is being played through pcm1. OBS sees this (or whatever OBS does, it manages to record my desktop audio). Audacity does not.

### Steps to reproduce

1. On FreeBSD (my system is 15.1p1),
2. pkg install audcity
3. Choose an output-only audio device (like optical or, I assume, coax) for output of other applications.
4. Attempt to get audacity to record that output.

### Expected behavior

Recording works?

### Actual behavior

No option for recording works.

### Audacity Version

Audacity 3.7.8

### Operating system

Other

### Additional context

_No response_

Start by reproducing the issue on FreeBSD 15.1p1 in plain OSS mode, using the devices listed by /dev/sndstat and checking whether pcm1 exposes the playing output. Compare Audacity's available recording devices with what OBS can capture; done means an output-only monitor port is visible in Audacity and can record desktop audio.

Written by the indexing model from the issue text.