The short-video algorithm figured out my fiancé had someone on the side before I did.   He'd gone to take measurements at the new home and left his phone on the couch.   I opened his short-video app and started scrolling. The first thing it recommended was a clip titled "How to Give Your 22-Year-Old Girlfriend a Princess Bedroom Fit for a 3-and-a-Half-Year-Old."   I opened the comments. His account was right at the top.   Caleb: [Anyone have a link to this exact star night-light? My baby gets scared sleeping alone. One with soothing sounds would be perfect.]   I turned to look at our new home, freshly renovated in minimalist black and gray.   Last month, I'd wanted to buy a plush throw pillow. He had frowned, called it childish, and insisted on returning it.   I kept scrolling. He'd liked reviews of couples' mystery boxes, amusement park guides, and period-cramp relief tips.   Every single like was timestamped late at night, during the same hours when he would turn his back to me, say he was exhausted from work, and go to bed early.   I closed the app and put his phone back where it had been.   Then I opened my email and replied to the message my supervisor had sent 3 days ago.   Natalie: Director Ellison, I'll take the 3-year overseas assignment in Asterford. I can leave as soon as I finish the handover next week.