Schema validation and error mapping

1) Where do Schema errors go?

Form writes “Schema decode/validation errors” into the errors.$schema branch, separating them from rule errors (errors.*) and manual errors (errors.$manual.*).

In UI, useField reads errors by priority:

1. errors.$manual.<path>
2. errors.<path> (rule errors)
3. errors.$schema.<path> (Schema errors)

2) Manually mapping Schema errors (optional)

If you need to “decode manually and write errors back” in some scenarios, use Form.SchemaErrorMapping:

const writes = Form.SchemaErrorMapping.toSchemaErrorWrites(schemaError, {
  // Optional: rename when schema field names differ from form field names
  rename: { amount: "amountText" },
  toLeaf: () => "Invalid field",
})

for (const w of writes) {
  dispatch({ _tag: "setValue", payload: { path: w.errorPath, value: w.error } })
}

This generates error paths aligned with the $list/rows[] convention (e.g. array indices are mapped into rows).