feat(taste): time-of-day / weekday context conditioning — #1531

Milestone #160 Opt 3 (temporal half). A new additive scoring term that
boosts a candidate when its artist's play history concentrates in the
CURRENT daypart × weekday-type cell, in the user's local timezone.

- Migration 0046: recommendation_weight_profiles.context_time_weight
  (per-profile scoring weight, DEFAULT 1.0).
- Query ListArtistContextPlayCountsForUser: per-artist completed-play
  counts split by the current cell (daypart night[22,5)/morning[5,12)/
  afternoon[12,17)/evening[17,22) × weekday-vs-weekend) via
  started_at AT TIME ZONE users.timezone; 365-day window, skips excluded.
- internal/recommendation/context.go: LoadContextAffinity computes each
  artist's shrunk cell-share minus the user's baseline share, clamped to
  [-1,1]; sparse artists shrink toward baseline (pseudo-count 5), unknown
  artists → 0 (cold-start neutral).
- Score() gains context_affinity_score · ContextTimeWeight; both
  candidate loaders set it per candidate.
- Tuning lab: ContextTimeWeight threaded through recsettings + admin API
  + web card ("Time-of-day weight" row) + Go/web tests. Shipped 1.0 both
  profiles (uniform start, re-bakeable).

Device-class axis deferred to #1551 (needs a client_id → device-class
mapping that doesn't exist yet).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/recsettings/patch.go

@@ -67,6 +67,10 @@ var weightFields = map[string]weightField{
 		get: func(w recommendation.ScoringWeights) float64 { return w.TasteWeight },
 		set: func(w *recommendation.ScoringWeights, v float64) { w.TasteWeight = v },
 	},
+	"context_time_weight": {
+		get: func(w recommendation.ScoringWeights) float64 { return w.ContextTimeWeight },
+		set: func(w *recommendation.ScoringWeights, v float64) { w.ContextTimeWeight = v },
+	},
 }
 
 // applyWeightPatch validates and applies a partial update, returning

internal/recsettings/service.go

@@ -54,16 +54,19 @@ type TasteTuning struct {
 // here from config.RecommendationConfig — YAML is bootstrap-only,
 // rule: config in UI). Radio is seed-directed (the user picked a
 // direction), so taste is a lighter nudge than in the daily mixes.
+// ContextTimeWeight starts uniform (1.0) across both profiles pending
+// trend data (#1531); split them once the metrics view justifies it.
 func ShippedRadioWeights() recommendation.ScoringWeights {
 	return recommendation.ScoringWeights{
-		BaseWeight:       1.0,
-		LikeBoost:        2.0,
-		RecencyWeight:    1.0,
-		SkipPenalty:      1.0,
-		JitterMagnitude:  0.1,
-		ContextWeight:    2.0,
-		SimilarityWeight: 2.0,
-		TasteWeight:      1.0,
+		BaseWeight:        1.0,
+		LikeBoost:         2.0,
+		RecencyWeight:     1.0,
+		SkipPenalty:       1.0,
+		JitterMagnitude:   0.1,
+		ContextWeight:     2.0,
+		SimilarityWeight:  2.0,
+		TasteWeight:       1.0,
+		ContextTimeWeight: 1.0,
 	}
 }
 
@@ -71,14 +74,15 @@ func ShippedRadioWeights() recommendation.ScoringWeights {
 // Must stay in sync with the pre-push literal in playlists/system.go.
 func ShippedDailyMixWeights() recommendation.ScoringWeights {
 	return recommendation.ScoringWeights{
-		BaseWeight:       1.0,
-		LikeBoost:        2.0,
-		RecencyWeight:    1.0,
-		SkipPenalty:      2.0,
-		JitterMagnitude:  0.1,
-		ContextWeight:    0.5,
-		SimilarityWeight: 1.5,
-		TasteWeight:      1.5,
+		BaseWeight:        1.0,
+		LikeBoost:         2.0,
+		RecencyWeight:     1.0,
+		SkipPenalty:       2.0,
+		JitterMagnitude:   0.1,
+		ContextWeight:     0.5,
+		SimilarityWeight:  1.5,
+		TasteWeight:       1.5,
+		ContextTimeWeight: 1.0,
 	}
 }
 
@@ -348,41 +352,44 @@ func (s *Service) audit(
 
 func upsertParams(profile string, w recommendation.ScoringWeights) dbq.UpsertWeightProfileDefaultsParams {
 	return dbq.UpsertWeightProfileDefaultsParams{
-		Profile:          profile,
-		BaseWeight:       w.BaseWeight,
-		LikeBoost:        w.LikeBoost,
-		RecencyWeight:    w.RecencyWeight,
-		SkipPenalty:      w.SkipPenalty,
-		JitterMagnitude:  w.JitterMagnitude,
-		ContextWeight:    w.ContextWeight,
-		SimilarityWeight: w.SimilarityWeight,
-		TasteWeight:      w.TasteWeight,
+		Profile:           profile,
+		BaseWeight:        w.BaseWeight,
+		LikeBoost:         w.LikeBoost,
+		RecencyWeight:     w.RecencyWeight,
+		SkipPenalty:       w.SkipPenalty,
+		JitterMagnitude:   w.JitterMagnitude,
+		ContextWeight:     w.ContextWeight,
+		SimilarityWeight:  w.SimilarityWeight,
+		TasteWeight:       w.TasteWeight,
+		ContextTimeWeight: w.ContextTimeWeight,
 	}
 }
 
 func updateParams(profile string, w recommendation.ScoringWeights) dbq.UpdateWeightProfileParams {
 	return dbq.UpdateWeightProfileParams{
-		Profile:          profile,
-		BaseWeight:       w.BaseWeight,
-		LikeBoost:        w.LikeBoost,
-		RecencyWeight:    w.RecencyWeight,
-		SkipPenalty:      w.SkipPenalty,
-		JitterMagnitude:  w.JitterMagnitude,
-		ContextWeight:    w.ContextWeight,
-		SimilarityWeight: w.SimilarityWeight,
-		TasteWeight:      w.TasteWeight,
+		Profile:           profile,
+		BaseWeight:        w.BaseWeight,
+		LikeBoost:         w.LikeBoost,
+		RecencyWeight:     w.RecencyWeight,
+		SkipPenalty:       w.SkipPenalty,
+		JitterMagnitude:   w.JitterMagnitude,
+		ContextWeight:     w.ContextWeight,
+		SimilarityWeight:  w.SimilarityWeight,
+		TasteWeight:       w.TasteWeight,
+		ContextTimeWeight: w.ContextTimeWeight,
 	}
 }
 
 func weightsFromRow(r dbq.RecommendationWeightProfile) recommendation.ScoringWeights {
 	return recommendation.ScoringWeights{
-		BaseWeight:       r.BaseWeight,
-		LikeBoost:        r.LikeBoost,
-		RecencyWeight:    r.RecencyWeight,
-		SkipPenalty:      r.SkipPenalty,
-		JitterMagnitude:  r.JitterMagnitude,
-		ContextWeight:    r.ContextWeight,
-		SimilarityWeight: r.SimilarityWeight,
-		TasteWeight:      r.TasteWeight,
+		BaseWeight:        r.BaseWeight,
+		LikeBoost:         r.LikeBoost,
+		RecencyWeight:     r.RecencyWeight,
+		SkipPenalty:       r.SkipPenalty,
+		JitterMagnitude:   r.JitterMagnitude,
+		ContextWeight:     r.ContextWeight,
+		SimilarityWeight:  r.SimilarityWeight,
+		TasteWeight:       r.TasteWeight,
+		ContextTimeWeight: r.ContextTimeWeight,
 	}
 }