Carousel buttons have the wrong or missing screen-reader label

• Where: carousel_previous.rb renders span.sr-only "Next slide";
  carousel_next.rb renders no sr-only span at all. Snapshot
  carousel/vertical line 17.
• Effect: a screen reader announces the previous button as "Next slide"
  and the next button as unlabeled.
• Fix: "Previous slide" on the previous button, add "Next slide" to the
  next button; re-record (on the 2.0 line) carousel/*.

Surfaced by the golden HTML suite (PR #536), which pins what 1.6 renders today — this defect included. Per maintainer decision (2026-09-19) main stays as is: this is addressed on the 2.0 line, and the golden snapshot that pins it is re-recorded there with the diff reviewed.

Source: design/v2/follow-up-issues.md.

Inizia da carousel_previous.rb e carousel_next.rb, poi esamina lo snapshot carousel/vertical alla riga 17 e gli altri snapshot golden di carousel/* sulla linea 2.0. Esegui la suite HTML golden e registra nuovamente carousel/*; il lavoro è completo quando i pulsanti precedente e successivo hanno le etichette corrette per gli screen reader e il diff dello snapshot esaminato le riflette.