flutter-perf-build-and-rebuild

Use when a screen rebuilds too much, a toggle or search input rebuilds a whole page, or build() does computation. Fixes expensive work inside Flutter build() methods and over-broad rebuilds: repeated sorting/filtering/formatting in build, widget-returning helper methods, missing const, builder widgets rebuilding static children, and state subscriptions (Riverpod select, Consumer, scoped providers) that rebuild too much. Do not use for list construction (flutter-perf-lists-and-scrolling) or derived-state caching (flutter-perf-derived-state).