Clamp the default buffer size to what the device supports

[benface]

from_device picks a 50 ms buffer without checking what the device accepts. My AirPods only take 15–960 frames, so it asks for 2048, and cpal 0.18 refuses a fixed size outside the supported range — the stream never opens.

open_default_sink then walks the other devices and takes the first that opens. On my machine that's a virtual output from a screen recorder, so the audio plays somewhere nobody can hear. That part surprised me more than the failure itself.

The range is already in default_config, so this clamps to it. OutputConfig::from in the speakers API does the same thing, just spelled out over four match arms.

Might be #900 as well — same "worked on crates.io, unsupported device on master" shape, on Windows.