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/0047_taste_profile_moods.up.sql

@@ -1,11 +1,11 @@
--- 0047_taste_profile_moods.up.sql — mood taste facet (#1534, milestone #160
--- Opt 2b). A fourth taste facet alongside artists + tags + eras: signed weights
--- over canonical mood buckets (melancholic / energetic / chill / …) derived
--- from a track's enriched folksonomy tags (#1490) via the internal/mood
--- vocabulary, rebuilt daily. Weight is a signed float — positive = drawn to
--- that mood, negative = passively avoided. Coverage is partial (grows with tag
--- enrichment), so it's a supplement, not a foundation. Mirrors
--- taste_profile_tags: CASCADE on user delete, indexed by (user_id, weight DESC).
+-- 0047_taste_profile_moods.up.sql — mood taste facet. A fourth taste facet
+-- alongside artists + tags + eras: signed weights over canonical mood buckets
+-- (melancholic / energetic / chill / …) derived from a track's enriched
+-- folksonomy tags via the internal/mood vocabulary, rebuilt daily. Weight is a
+-- signed float — positive = drawn to that mood, negative = passively avoided.
+-- Coverage is partial (grows with tag enrichment), so it's a supplement, not a
+-- foundation. Mirrors taste_profile_tags: CASCADE on user delete, indexed by
+-- (user_id, weight DESC).
 CREATE TABLE taste_profile_moods (
     user_id    uuid             NOT NULL REFERENCES users(id) ON DELETE CASCADE,
     mood       text             NOT NULL,