Keep yield alerts open until quality recovers

A yield alert could close itself while the line was still failing. The drop that raised it slowly became part of the baseline it was being compared against, so a single quality incident produced a string of alerts opening and closing on their own — one incident on a production line generated nine.

• Fixed yield alerts closing on the very failures that raised them, so one incident now stays one alert until someone resolves it
• Locked each alert to the baseline measured when it was raised, so the bar to close it no longer drifts while the incident is still open
• Applied the same rule to custom yield rules, which recalculated their reference window on every check