_saveCoverArt and _saveLyrics repeated the same SAF/local publish
skeleton: render into a temp dir and publish it to the download tree
with createSafFileFromPath (or write next to the audio file), clean the
temp dir, then report the outcome. Move that skeleton into
_publishSidecarFile with parameters for the temp prefix, extension, mime
type, success message and whether a snackbar hides the current one.
Each caller keeps its own try/catch, base name, lyrics progress
snackbar and the render step. The cover render returns null after its
no-source snackbar so the helper stops at the same point as before
(without deleting the temp dir, as before). Await order, mounted checks,
messages and cleanup placement are unchanged.
zarzet
ff3f752014