docs: server comments say what the code does, not how it came to be (#6277)

Comment blocks in cmd/minstrel and 30 smaller internal packages, rewritten
to rule 32's standard with each citation read in context: task, milestone
and rule ids go, and so do the stories they were attached to ("used to",
"Before #N", measurements from one install, quotes, pointers to Fabled
Librarian's records and to docs/superpowers files that are not in the
repo). Where a story wrapped a real constraint, the constraint stays as a
present-tense fact.

Comments that had gone stale are corrected:
- taste.Config: the tuned values are overlaid by internal/recsettings;
  it is no longer "a later follow-up".
- StorageConfig: the data dir holds art, caches and the stream secret,
  not only playlist covers.
- the Subsonic album list and getUser comments describe what they do
  today rather than a milestone that would change it.

Checked: the non-comment token stream of every changed file matches
HEAD, and gofmt -l is empty.

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

internal/similarity/worker.go

@@ -5,14 +5,14 @@
 //
 // For recordings it keeps LB's whole answer in listenbrainz_similar_recordings
 // and derives the track_similarity edges from it in SQL, against whatever is
-// in the library at the time (#5296). Matching once at fetch time missed every
-// recording that reached the library afterwards, through an import or an MBID
-// the AcoustID lookup filled in. For artists it stores the in-library matches in
-// artist_similarity and the rest in artist_similarity_unmatched, as before.
+// in the library at the time, so a recording that reaches the library later
+// (an import, or an MBID the AcoustID lookup fills in) gains its edges without
+// asking LB again. For artists it stores the in-library matches in
+// artist_similarity and the rest in artist_similarity_unmatched.
 //
 // Every answer is recorded as a fetch, an empty one included, and the queue
-// reads those records: freshness used to be read from the edges, so a seed
-// that matched nothing was never fresh and held the head of the queue.
+// reads those records rather than the edges: a seed that matched nothing is
+// still fresh and does not hold the head of the queue.
 package similarity
 
 import (
@@ -200,8 +200,8 @@ func (w *Worker) upsertArtistSimilar(ctx context.Context, q *dbq.Queries, artist
 	}
 	sort.Slice(results, func(i, j int) bool { return results[i].Score > results[j].Score })
 	// Scores are stored relative to the seed's closest artist, as track edges
-	// are (#6177): LB's raw scores are counts (16 to 10,875 on the operator's
-	// library), and both the candidate pool and the suggestions read 0 to 1.
+	// are: LB's raw scores are unbounded counts, and both the candidate pool
+	// and the suggestions read 0 to 1.
 	best := results[0].Score
 
 	mbids := make([]string, 0, len(results))

internal/similarity/worker_integration_test.go

@@ -209,9 +209,9 @@ func TestTickOnce_MapsLBResponseToLocalLibrary(t *testing.T) {
 	}
 }
 
-// LB's scores are counts, not 0 to 1 (16 to 1445 on the operator's library).
-// An edge is stored over the seed's best score in the whole answer, in the
-// library or not, so the scorer reads it as 0 to 1 (#6177).
+// LB's scores are counts, not 0 to 1. An edge is stored over the seed's best
+// score in the whole answer, in the library or not, so the scorer reads it as
+// 0 to 1.
 func TestTickOnce_EdgeIsRelativeToTheSeedsBest(t *testing.T) {
 	f := newFixture(t)
 	mbidA := "11111111-1111-1111-1111-111111111111"
@@ -241,8 +241,8 @@ func TestTickOnce_EdgeIsRelativeToTheSeedsBest(t *testing.T) {
 	}
 }
 
-// The 20-per-seed cap is gone with the cache (#5296): LB's answer is at most
-// 50, and every recording of it that is in the library becomes an edge.
+// LB's answer is at most 50, and every recording of it that is in the library
+// becomes an edge: no per-seed cap.
 func TestTickOnce_KeepsEveryInLibraryMatch(t *testing.T) {
 	f := newFixture(t)
 	mbidSeed := "11111111-1111-1111-1111-111111111111"
@@ -311,7 +311,7 @@ func TestTickOnce_RefreshesStaleRow(t *testing.T) {
 	_ = f.pool.QueryRow(context.Background(),
 		`SELECT score, fetched_at FROM track_similarity WHERE track_a_id = $1 AND track_b_id = $2 AND source = 'listenbrainz'`,
 		trackA.ID, other.ID).Scan(&score, &fetchedAt)
-	// The seed's only answer is its best, so the refreshed edge is 1.0 (#6177).
+	// The seed's only answer is its best, so the refreshed edge is 1.0.
 	if score != 1.0 {
 		t.Errorf("score = %v, want 1.0 (refreshed, relative to the seed's best)", score)
 	}
@@ -452,7 +452,7 @@ func TestUpsertArtistSimilar_PersistsUnmatchedToTable(t *testing.T) {
 	w := newTestWorker(f, "")
 
 	similars := []listenbrainz.SimilarArtist{
-		// LB's scores are counts; rows are stored over the seed's best (#6177).
+		// LB's scores are counts; rows are stored over the seed's best.
 		{MBID: inLibMBID, Name: "InLib Artist", Score: 1000},
 		{MBID: "out-mbid-1", Name: "Outsider One", Score: 850},
 		{MBID: "out-mbid-2", Name: "Outsider Two", Score: 800},
@@ -543,9 +543,9 @@ func recordingLB(answer func(mbid string) string) (*httptest.Server, func() []st
 	}
 }
 
-// The starvation #3879 measured: a seed whose answer matched nothing in the
-// library wrote nothing, stayed due, and was asked again every tick ahead of
-// everything behind it. Recording the fetch moves the queue on.
+// A seed whose answer matches nothing in the library writes no edges, and
+// must still leave the head of the queue: recording the fetch moves it on,
+// so it is not asked again every tick ahead of everything behind it.
 func TestTickOnce_UnmatchedAnswerDoesNotHoldTheQueue(t *testing.T) {
 	f := newFixture(t)
 	mbids := []string{
@@ -583,7 +583,7 @@ func TestTickOnce_UnmatchedAnswerDoesNotHoldTheQueue(t *testing.T) {
 	}
 }
 
-// The point of the cache (#5296): a recording LB named while it was not in the
+// The point of the cache: a recording LB named while it was not in the
 // library becomes an edge once it arrives, on the next tick's resolve, without
 // asking LB again. One edge per recording when the library holds two copies,
 // and none to a copy that is missing.