docs: api comments say what the endpoints do, not how they came to be (#6277)

Rewrites the internal/api comment blocks to rule 32: task, milestone and
rule ids gone, the stories behind them restated as the constraint they
left, stale references corrected (the stream secret is wired from config,
the timezone handler already refreshes the scheduler, the Android app is
the native client, the design docs cited are not in the repo). Also
rewraps comment lines over 80 columns left by the earlier batches.

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

internal/api/catalogue.go

@@ -36,9 +36,10 @@ type catalogueSearchResult struct {
 	Requested     bool   `json:"requested"`
 }
 
-// handleCatalogueSearch implements GET /api/catalogue/search?q=&kind=artist|album|track
-// (M502 #5519), asking MusicBrainz directly. An unreachable MusicBrainz is a
-// 503 the page shows as such (rule 164).
+// handleCatalogueSearch implements GET
+// /api/catalogue/search?q=&kind=artist|album|track asking MusicBrainz directly.
+// An unreachable MusicBrainz is a 503 the page shows as such, not an empty
+// result.
 func (h *handlers) handleCatalogueSearch(w http.ResponseWriter, r *http.Request) {
 	kind := strings.TrimSpace(r.URL.Query().Get("kind"))
 	switch kind {
@@ -250,7 +251,7 @@ func (h *handlers) catalogueInLibrary(ctx context.Context, kind, mbid string) (b
 
 // handleCatalogueArt implements GET /api/catalogue/art/{kind}/{mbid} for an
 // artist or a release group Minstrel doesn't hold. The image comes from the
-// operator's enabled cover-art sources and is kept on disk, so the browser
+// enabled cover-art sources and is kept on disk, so the browser
 // never fetches a third-party host. A 404 shows the placeholder.
 func (h *handlers) handleCatalogueArt(w http.ResponseWriter, r *http.Request) {
 	kind, mbid := chi.URLParam(r, "kind"), chi.URLParam(r, "mbid")