Release v2.6.0

Added

• Collapse on narrow screens (opt-in, spec 004-collapse-narrow): GitHub-style trail on phones. Below a width breakpoint the trail shows a "…" button, one separator and the current crumb (one line, ellipsis); the "…" button opens a dropdown with every previous crumb (same labels, icons and links; non-link crumbs as text). Above the breakpoint the trail is unchanged. See USAGE.
  • Global config presentation.collapse (enabled false, min_items 3, breakpoint 40rem; collapse: true shorthand; invalid breakpoints and min_items < 2 rejected at container build).
  • Per collection responsiveConfig.collapse: true / false or { "enabled", "min_items", "breakpoint" } merged key by key over the global value (invalid stored values are ignored).
  • Markup: data-breadcrumb-collapse on .breadcrumb-kit, li.breadcrumb-collapse before the last separator with a <details> / <summary> disclosure (aria-label "Show previous pages", visible "…") and ol.breadcrumb-collapse__menu[role=list]. Normal items stay in the DOM.
  • Nonce-stamped styles: container query on the wrapper (@container breadcrumb-kit) with a viewport media query fallback, --breadcrumb-kit-collapse-* theming tokens with system-colour (light / dark) fallbacks, reduced-motion aware.
  • js/breadcrumb-collapse.js (external, defer, no inline handlers): Escape closes and returns focus to "…", outside click and choosing a link close. Works without JavaScript.
  • Overridable partials _breadcrumb_collapse.html.twig and _breadcrumb_collapse_assets.html.twig; BreadcrumbCollapse DTO, BreadcrumbTrailView::$collapse and isCollapsible() (Twig trail.collapsible).
  • Translations breadcrumb.collapse.toggle / breadcrumb.collapse.menu in en, es, de, fr, it, nl, pt.
• Demo: the default collection enables the collapse below 40rem (try /en/demo/deep/s1/s2/s3/s4/s5/s6 at phone width).

Unchanged

• With the option off (default), or for trails shorter than min_items, breadcrumb.html.twig renders byte-identical HTML to 2.5.0 (tested against the 2.5.0 template).