Fold the three AllowsMediaDownloadControls copies into
HistoryItem::allowsMediaDownloadControls, share one retry-or-fail
handler in SendMusicSelectionBatch, reuse MakeMusicSelectionItems
instead of the NormalizeSelections near-copy and extract the
duplicated bot resolution block into applyResolvedBot.
Remove the dead accumulate-from-top machinery from both music
providers and the list widget, the subscriber-less slice snapshot
stream, the never-started search section request timer and the
unused Result::isAudioResult.
Consolidate the sixteen MusicAttachBox make_state allocations into
one State struct, fix the include order, use base::take for the
request waiters, replace the removeFromAlbum if-with-initializer
with a plain null-checked session and type kSearchRequestDelay as
crl::time.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
