docs: migration headers keep the before and after, without ids, quotes or one library's numbers (#6277)

Applies rule 32's migration exception: each header still says what the
schema was, what changes and what it prevents, but task, milestone,
decision and rule ids are replaced by the practice they stood for, the
operator quotes by the decision, single-install counts are dropped, and
pointers to a deleted package and an external design doc are gone.
golang-migrate keeps no checksum, so editing applied migrations'
comments is safe.

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

internal/db/migrations/0081_wanted.up.sql

@@ -1,4 +1,4 @@
--- 0081_wanted.up.sql — the wanted list (Scribe milestone #502, #5520).
+-- 0081_wanted.up.sql — the wanted list.
 --
 -- With Lidarr gone, Minstrel keeps its own record of what it is looking for:
 --
@@ -19,7 +19,7 @@
 -- lidarr_requests becomes requests with no Lidarr columns: approving a request
 -- now records a want or a follow instead of sending an add to Lidarr. The
 -- missing-file sweeper's attempt bookkeeping goes too; retrying belongs to the
--- search schedule (#5521), which works per want.
+-- search schedule, which works per want.
 
 CREATE TABLE release_type_profiles (
     id              uuid PRIMARY KEY DEFAULT gen_random_uuid(),
@@ -36,8 +36,8 @@ CREATE TABLE release_type_profiles (
 CREATE UNIQUE INDEX release_type_profiles_one_default
     ON release_type_profiles (is_default) WHERE is_default;
 
--- Lidarr's "Standard" metadata profile, which every followed artist used
--- (note #5527): albums, EPs and singles, studio releases only.
+-- Lidarr's "Standard" metadata profile, which followed artists used: albums,
+-- EPs and singles, studio releases only.
 INSERT INTO release_type_profiles (name, primary_types, secondary_types, is_default)
 VALUES ('Standard', ARRAY['Album', 'EP', 'Single'], '{}', true);
 
@@ -53,7 +53,7 @@ CREATE TABLE follows (
     baseline_at timestamptz,
     -- Whether the baseline also wants what the artist had already released
     -- that the profile passes and the library lacks: an approved artist
-    -- request, or the operator ticking "also want…". Cleared once applied.
+    -- request, or an admin ticking "also want…". Cleared once applied.
     want_existing boolean NOT NULL DEFAULT false,
     -- The discography read this follow last applied.
     checked_at  timestamptz,
@@ -111,7 +111,7 @@ ALTER INDEX lidarr_requests_status_idx RENAME TO requests_status_idx;
 ALTER INDEX lidarr_requests_artist_mbid_idx RENAME TO requests_artist_mbid_idx;
 ALTER INDEX lidarr_requests_album_mbid_idx RENAME TO requests_album_mbid_idx;
 
--- Requests made before #5241 name albums by release id. A want is keyed by
+-- Older requests may name albums by release id. A want is keyed by
 -- release group, so repoint every request the library can translate.
 UPDATE requests r
    SET album_mbid = a.release_group_mbid,
@@ -133,10 +133,10 @@ SELECT DISTINCT ON (r.album_mbid)
  ORDER BY r.album_mbid, r.requested_at
 ON CONFLICT (release_group_mbid) DO NOTHING;
 
--- The library's album artists start out followed on the default profile
--- (operator, 2026-10-09: "we already have artists in minstrel those start as
--- the wanted artists"). Various Artists and MusicBrainz's bracketed
--- placeholders ([unknown], [anonymous]…) are not artists anyone follows.
+-- The library's album artists start out followed on the default profile: the
+-- artists already in the library are the wanted artists. Various Artists and
+-- MusicBrainz's bracketed placeholders ([unknown], [anonymous]…) are not
+-- artists anyone follows.
 INSERT INTO follows (artist_mbid, artist_name, profile_id)
 SELECT ar.mbid, ar.name, p.id
   FROM artists ar