Field events are not cancelable, and carry the value alone

jolly-input fires continuously during interaction and jolly-change on commit; both bubble, are composed, and carry { value } and nothing else. Neither is cancelable: elements are forbidden from mutating themselves (ADR-0002), so there is nothing for preventDefault() to prevent, and a cancelable event that ignores cancellation is a trap.

A field's revert affordance is not a third kind of change — it commits default through jolly-change, keeping one write-back path. Pane-level events (jolly-reorder, jolly-revert) carry keys instead.

Considered Options

• A source discriminator on the change detail. jolly-input against jolly-change already separates continuous from committed, which is the distinction consumers ask for.
• The element writing its own error. It would replace a consumer's validation message on the first typo and clear it afterwards, so the consumer cannot trust a property it set. Parse failures use a private #parseError that takes display precedence instead.
• A jolly-error event with no local rendering. Every numeric field needs the same write-back boilerplate, and forgetting it makes a typo do nothing at all.