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/exchange/exchange.go

@@ -1,7 +1,6 @@
 // Package exchange talks to FabledExchange's native API for the two jobs that
-// are not downloading (M502 #5518): searching its DHT index (/api/search) and
-// describing one torrent (/api/torrents/{infohash}). Downloading is
-// internal/downloader's. Ported from Fabled Librarian's internal/exchange.
+// are not downloading: searching its DHT index (/api/search) and describing
+// one torrent (/api/torrents/{infohash}). Downloading is internal/downloader's.
 //
 // The native search rather than Exchange's Torznab feed, because it reports
 // whether a swarm was measured and how many files a torrent holds, which the