error-handling-typed-results

From the author

Enforces a typed-error spine — a hand-rolled sealed Result<T,F> plus one per-boundary sealed Failure carrying a stable code and typed params (never a localized string), returned instead of thrown; recoverable failures are values, only bugs throw. Convert-at-boundary catches narrowly with an on-clause and logs the original error+stack BEFORE returning a typed Failure; call sites switch exhaustively with no default:; the taxonomy of what the global error net (FlutterError.onError + PlatformDispatcher.onError, installed by app-startup-and-bootstrap) routes into, plus Isolate.run re-wrapping; mechanism selection (Error vs assert vs Exception vs sealed outcome) and @useResult; and a never-lose-data layer (one-transaction-per-mutation, debounced autosave drafts, optimistic soft-delete/Undo). Use when writing result.dart/failures.dart, a try/catch or sealed-switch default:, wiring bootstrap handlers, a repository/service/DAO boundary, or transactions, drafts, or soft-delete/Undo.