Loudness Auto-Match metered every clip as the stereo pair clip_signal
plays, so a mono source (or a mono pick from Modify > Audio Channels /
Breakout to Mono), copied onto both sides, read 3.01 LU louder than the
file and got 3 dB too little gain. BS.1770 and ffmpeg's ebur128 measure
a mono programme as one channel; now so does clip_loudness, through a new
render::audio::clip_is_mono. Stereo and wider sources are unchanged, as
are the export loudness pass and the Meters panel (they measure the real
output mix).
Regression test: the same speech as a 1-channel WAV and as dual-mono
stereo measure 3.01 LU apart, the mono clip agrees with a one-channel
meter over the file within 0.1 LU, and a mono pick counts as mono.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
