What does flutter-development-guide do?
Flutter implementation and review checklist. Use only when writing, modifying, or reviewing Flutter widget code, layout constraints, adaptive sizing, navigation and routing, platform channels, platform views, background entry points, list and image performance, async gaps across BuildContext, disposal, theme and design tokens, accessibility, localization, offline and error states, or Flutter test and golden coverage. Do not use for Dart language generalities, native Android or iOS internals beyond the engine and channel-registration seam a Dart entry point depends on, or broad rewrites.