Built is not shipped. Between a merged pull request and a decent release sits the work everyone is too tired to do properly: opening the real thing, on a real device, and looking at it.
Run a design QA pass on the build itself — the installed app, the deployed staging site — never on a screenshot or the prototype. Go screen by screen with your spec open. Force the documented states instead of hoping: empty the test account, throttle the network to hold the loading state, point the client at a dead endpoint for the error. Read the copy as you go — placeholder text and wrong labels survive code review, where people read diffs, not sentences. Check the long names, the small screen, the dark theme, the keyboard-only path.
File what you find as tickets with a severity, not as grievances in a thread. Separate "this is broken" from "this is four pixels out". Engineers fix both when you are honest about which is which, and neither when everything is marked urgent.
Agree what blocks release before you start looking, and write the line down: data loss, a blocked main task, the wrong words in front of a customer. Everything else waits a week. A bug list with no threshold is just a negotiation, and you lose that one at six o'clock on launch day.