Cut drift alert noise to one alert per event

One production incident — a failing fixture, a drifting environment — used to raise a separate drift alert for every affected measurement, and brief wobbles could alert and resolve within minutes.

• Grouped automatic drift alerts into one event per procedure and part: every drifting measurement attaches to the same alert with its own timeline, and same-day recurrences reopen it instead of opening a duplicate. Custom alert rules are unchanged.
• Added persistence gates: a drift now has to hold across consecutive runs before it alerts — and before it auto-resolves — ending one-off wobble alerts and resolve/reopen flapping. Sudden critical shifts still fire immediately.
• Added an instrument-resolution floor: a shift smaller than the measurement device's own step no longer alarms, silencing last-digit noise on quantized sensors.