Closes Fable #414. forYouHeadN/forYouTailN go 12/13 → 50/50 so the
For-You snapshot is 100 tracks, matching Discover. Motivated by the
shuffle-on-play default that just shipped (#413): a 25-track shuffle
pool repeats fast; 100 makes re-plays within a day feel varied.
pickHeadAndTail already degrades gracefully when the candidate pool
is too thin for a full head/tail split (returns top-N-by-score),
mirroring how Discover returns <100 when its buckets are thin — no
new edge-case handling needed. No build-path test asserts the
For-You total; pickHeadAndTail unit tests pass their own head/tail
values so they're unaffected.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen
69569a5c2b