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/indexer/indexer.go

@@ -1,5 +1,5 @@
 // Package indexer is what every search source answers with, and the Torznab
-// client (M502 #5518). Ported from Fabled Librarian's internal/indexer.
+// client.
 //
 // A client here holds ONE endpoint and knows nothing about the others. The
 // fan-out across sources, the merge and what a source being down means belong
@@ -7,9 +7,8 @@
 // about one source.
 //
 // Prowlarr is not served from here: it has no aggregate Torznab feed (`all`
-// 404s like any id it does not have, measured by Fabled Librarian, #4304), so
-// asking it everything at once means its native API, which internal/prowlarr
-// speaks.
+// 404s like any id it does not have), so asking it everything at once means
+// its native API, which internal/prowlarr speaks.
 package indexer
 
 import (
@@ -34,7 +33,7 @@ var ErrUnreachable = errors.New("indexer unreachable")
 // field in Settings, an outage is something to wait out.
 var ErrAuth = errors.New("the API key was refused")
 
-// UserAgent names Minstrel in the operator's own Prowlarr and indexer logs.
+// UserAgent names Minstrel in Prowlarr's and each indexer's logs.
 const UserAgent = "Minstrel (self-hosted music server; release search)"
 
 // MusicCategories are the Newznab categories a music search asks for: 3000