Name the reaper's hard delete in the event body comments (closes #455)

The comments on eventBodyQuery and on its reaped-event test credited
the deleted_at predicate with refusing a reaped event. The retention
reaper deletes event rows outright, so a reaped event is simply gone;
nothing soft-deletes an event, so the predicate excludes nothing today
and the test's soft-delete case only pins it.

Model: opus-5-5

internal/handlers/event_body_test.go

@@ -405,10 +405,11 @@ func TestHandleEventBodyDownload_UnknownEvent404s(t *testing.T) {
 // route. The body is read in one query before any header is
 // written, so a reaped event cannot produce a partial download:
 // it is a clean 404 with no Content-Length and no
-// Content-Disposition. Both removals the codebase performs are
+// Content-Disposition. The reaper deletes event rows outright,
-// covered — the reaper hard-deletes, and a soft-deleted row is
+// which is the "hard deleted" case. The "soft deleted" case
-// excluded by the query's own deleted_at predicate rather than
+// covers a row no code produces today: it only pins the query's
-// by GORM's default scope, which Raw bypasses.
+// own deleted_at predicate, the soft-delete condition Raw would
+// otherwise skip.
 func TestHandleEventBodyDownload_ReapedEvent404s(t *testing.T) {
 	t.Parallel()