A switch for what takes effect at once, with no save button (for a choice that only counts after saving, use a checkbox). It is a <button role="switch">: aria-checked says the state, the keyboard toggles it and the caller does the work in its own phx-click. By default it writes no hidden input, so it does not take part in a form's submit: the state is the LiveView's, kept by the click. Give it a name (the field mode) and it renders a hidden input <id>-field with "true" or "false", which the DevactionUI.Switch hook keeps the same as the button, firing input so the form's phx-change hears it; a press then works with no phx-click at all. While the change is being kept, saving puts a spinner in the thumb and the control ignores presses; saved_note/1 is the "saved now" the caller shows after.

Colors: the default ink, :ai (amber) and :ok (green). Sizes: :sm, :md, :lg. The track has a hit area of 44px high; in switch_row/1 and switch_card/1 the text is a <label>, so pressing it toggles too.