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/loudness.sql

@@ -1,5 +1,5 @@
 -- name: UpsertTrackLoudness :exec
--- Written when the backfill measures a track (#4995). Replaces the row
+-- Written when the backfill measures a track. Replaces the row
 -- wholesale: a measurement of the old bytes has no standing once the file has
 -- changed.
 INSERT INTO track_loudness (
@@ -78,7 +78,7 @@ UPDATE loudness_settings
 RETURNING *;
 
 -- name: ListAlbumsNeedingLoudness :many
--- The album pass's work queue (#4996): albums whose present tracks or their
+-- The album pass's work queue: albums whose present tracks or their
 -- measurements have changed since album loudness was last computed, or that
 -- never had it. The digest is over every present track's id and the
 -- measurement it holds at the current version ('-' for none), so a track
@@ -154,7 +154,7 @@ SELECT integrated_lufs, true_peak_dbtp FROM album_loudness WHERE album_id = $1;
 
 -- name: GetReplayGainByTrackIDs :many
 -- Track and album loudness for a set of tracks, for every surface that hands
--- gains to a client (#4997). A measurement from an older analysis version is
+-- gains to a client. A measurement from an older analysis version is
 -- still delivered: it is a better gain than none until the backfill redoes it.
 SELECT t.id,
        tl.integrated_lufs AS track_lufs,