Extract Audio now exists as a task, with recursion, multi-select scoping, a
format choice and multi-track handling — none of which the one-shot menu entry
had, since it always produced a single mp3.
/extract-audio stays because the file viewer's button plays its output rather
than saving it beside the video, but it no longer returns a cached file: like
transcription and OCR, it always redoes the work. The path is now named outRel,
since it is an output location rather than a cache.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>