Migrating from v1

v2 is a rewrite and does not run side by side with v1 wiring.

v1 pattern	v2 replacement
`UI.callback` string registry	direct event listeners and `ui-*` events
`data-modal-*` triggers	`ui-modal`, `UI.dialog`, invoker commands
delegated click setup	element methods and properties
DOM surgery and parent chains	`UI.create.*` or element APIs
manual toast region	`UI.toast()`
select data attributes	`ui-select.options` or `ui-option` children
details `data-open`	reflected `open` property

CSS class names, tokens and visual design are unchanged by intent.