The #843 fallback saved the discovery-cache match using the client's
original_artist verbatim — but the client sends a joined "A, B, C" string, while
EVERY in-memory + sync path keys the cache by the first artist (artists[0]). So a
multi-artist fix (the reporter's exact "Cherrymoon Traxx, Hermol, SBM, BELS"
case) would have saved under a key the sync never looks up — the fix would
"succeed" with no error but silently never apply.
Reduce the client artist to the first (split on comma) in the no-state branch so
its cache key matches the in-memory/sync convention exactly. Single-artist tracks
are unaffected.
Test: no-state save now keys by the first artist, and a new test pins that the
no-state and in-memory paths produce an IDENTICAL cache key for the same
multi-artist track. 74 discovery tests pass.
5bc27e6268