docs: query comments say what each query selects and why, not how it came to be (#6277)

Rewrites the internal/db/queries comments to rule 32 and regenerates
dbq, whose doc comments and embedded SQL carry them. The bugs behind the
tiered mixes, the md5 order seed, the score bands and the round-robin
arms are restated as the constraint each one enforces; counts from one
library and stale cross-references are gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/db/queries/recommendation_tuning.sql

@@ -1,9 +1,9 @@
--- Recommendation tuning lab queries (#1250). Seeding happens via the
+-- Recommendation tuning lab queries. Seeding happens via the
 -- recsettings boot reconcile; shipped defaults live in Go only.
 
 -- name: UpsertWeightProfileDefaults :exec
 -- Boot reconcile: insert the shipped defaults for a profile if the row
--- doesn't exist yet. Never overwrites operator-tuned values.
+-- doesn't exist yet. Never overwrites admin-tuned values.
 INSERT INTO recommendation_weight_profiles (
     profile, base_weight, like_boost, recency_weight, skip_penalty,
     jitter_magnitude, context_weight, similarity_weight, taste_weight,
@@ -54,8 +54,8 @@ UPDATE taste_tuning
 RETURNING *;
 
 -- name: UpsertDiscoverTuningDefaults :exec
--- Boot reconcile for the Discover scope (#2377). Never overwrites
--- operator-tuned values, same contract as the other two.
+-- Boot reconcile for the Discover scope. Never overwrites
+-- admin-tuned values, same contract as the other two.
 INSERT INTO discover_tuning (singleton, tag_overlap_weight, snooze_days)
 VALUES (true, $1, $2)
 ON CONFLICT (singleton) DO NOTHING;
@@ -77,7 +77,7 @@ INSERT INTO recommendation_tuning_audit (scope, action, changes)
 VALUES ($1, $2, $3);
 
 -- name: ListTuningAudit :many
--- Newest first; consumed by the metrics trend view (#1251) to annotate
+-- Newest first; consumed by the metrics trend view to annotate
 -- knob turns on the timeline.
 SELECT id, changed_at, scope, action, changes
   FROM recommendation_tuning_audit