Codegen and toolchain

Enforces a deterministic build_runner codegen discipline: run one pinned `dart run build_runner build --delete-conflicting-outputs` pass BEFORE `flutter analyze` (never after), fence every builder with `generate_for:` globs in a per-package `build.yaml`, make one deliberate commit-vs-gitignore decision for `*.g.dart`/`*.freezed.dart`/`*.drift.dart` and back it with the matching CI gate (freshness diff if committed, codegen-first if gitignored), mirror the generated-file globs into the analyzer AND coverage excludes, pin the SDK, and never hand-edit generated output. Use when editing build.yaml, analysis_options.yaml, pubspec.yaml, .gitignore, .gitattributes, or CI workflo…