Enforces Flutter runtime performance — const subtrees, minimal rebuild scope via ref.watch(select), lazy ListView/GridView builders and slivers, sized image decode (cacheWidth/ResizeImage), heavy work off the UI isolate via compute/Isolate, surgical RepaintBoundary, dispose everything, and measurement in profile mode on a floor device. Use when optimizing UI, diagnosing jank or dropped frames, tuning long lists or images, reviewing rebuild/repaint scope, or when the task mentions const, select, ListView.builder, cacheWidth, compute, RepaintBoundary, AnimatedBuilder, DevTools, raster thread, or 60/120fps.
