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/library_test.go

@@ -169,7 +169,8 @@ func TestHandleGetAlbum_NoTracks(t *testing.T) {
 	if len(got.Tracks) != 0 {
 		t.Errorf("tracks len = %d, want 0", len(got.Tracks))
 	}
-	// Year omitempty: releaseYear=0 => Year=0 => field should be absent from JSON
+	// Year omitempty: releaseYear=0 => Year=0 => field should be absent from
+	// JSON
 	if got.Year != 0 {
 		t.Errorf("year = %d, want 0", got.Year)
 	}
@@ -226,7 +227,8 @@ func TestHandleGetArtist_HappyPath(t *testing.T) {
 	if len(got.Albums) != 2 {
 		t.Fatalf("albums len = %d, want 2", len(got.Albums))
 	}
-	// ListAlbumsByArtist orders by release_date then sort_title; Abbey Road (1969) first.
+	// ListAlbumsByArtist orders by release_date then sort_title; Abbey Road
+	// (1969) first.
 	if got.Albums[0].Title != "Abbey Road" {
 		t.Errorf("first album = %q, want Abbey Road", got.Albums[0].Title)
 	}
@@ -475,10 +477,10 @@ func TestRoutesRegisteredInMount(t *testing.T) {
 		"/api/tracks/00000000-0000-0000-0000-000000000001",
 		"/api/tracks/00000000-0000-0000-0000-000000000001/stream",
 		"/api/search?q=x",
-		// Browse indexes (#367).
+		// Browse indexes.
 		"/api/library/genres",
 		"/api/library/years",
-		// Admin surfaces for the missing-file lifecycle (#2527). Both must
+		// Admin surfaces for the missing-file lifecycle. Both must
 		// 401 at the middleware rather than 404 — they live inside the
 		// admin group, so reaching the auth check is what proves they are
 		// wired.