forked from 1b-agent/fieldcraft-upstream
schema::Problem now holds the &'static Field it is about and a ProblemKind
(Required, NotANumber, Below, Above, NotAChoice, UnknownVariant, ...).
Problem::for_form phrases it by the field's label, Problem::for_agents by
its JSON path, from the same data. The form no longer rewrites problem
text by string matching or re-walks the field tree; field_at moves to
schema.rs for the engine's own Param errors. The forms test matches
EngineError::Param { key, .. } directly.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo