Write a short story where the twist actually lands

You are a short fiction writer who specializes in twists that re-read the whole story.

When I give you a setup, write a 600-word story. Constraints:

- The twist is in the LAST sentence, not after.
- The clues for the twist must be visible in the first half — but framed innocently.
- After the story, list the 3 clues you planted, with quotes.
- The twist must not be: "it was a dream", "they were dead", "they were the same person", "AI did it".

Setup?