Breadcrumb

The trail from root to current page, in order. Every item but the last needs an `href`; an ancestor without one, or with an empty-string `href`, renders as plain text (never an empty link); a plain ancestor has no anatomy part of its own — it is text inside `item` (a `<span>` with no data-part and no class on web and Lit, a Text with no testID on native) and takes `itemColor`; it needs no selector of its own, since the `item` part already selects its container. It renders no interactive element, so activating it fires no `onNavigate`. The last is the current page and its `href` is ignored. An empty array renders the named landmark around an empty list; a single item renders only the current page; neither raises a dev warning. Lit starts the property as `[]`. Export the item type as `BreadcrumbItem`.

Accessible name of the navigation landmark. Change it only if the page has another breadcrumb. `copy.navLabel` is the canonical string: the default is that copy key, not a second literal, so translating the copy block moves the default with it.

Accessibility: Rendered as aria-label on the nav so it is distinguished from other navigation landmarks.

When there are more than four items, show the first, an ellipsis, and the last two; the ellipsis is a button that reveals the rest. The rule is literal: five items hide the second and third. Once revealed the trail stays expanded for the life of the instance, even if `items` changes. That state is deliberately private: no prop or event exposes it, so it cannot be observed, persisted or reset, and a remount collapses the trail again. Set false for short trails that must always show in full.

Fired when a non-current item is activated, as `(item, index, event)` on web and `(item, index)` on native, where there is no event. On web the link still navigates unless the handler returns `false` or calls `event.preventDefault()`. On Lit, `preventDefault()` on the `navigate` CustomEvent or on `detail.originalEvent` both cancel (the first also prevents the original click). On native the handler is passed to Link as `onPress` and typed `boolean | void`: it is the navigation, so returning `false` has nothing to cancel (Breadcrumb links are never `external`); without a handler the Link falls back to Linking.openURL.