feat(Breadcrumbs): declarative compound component with overflow

[johnleider]

Summary

• New declarative Breadcrumbs architecture using Group + Overflow contexts
• Items/Dividers/Ellipsis register and self-measure
• Visibility controlled via selection state
• Ellipsis auto-hides when everything fits, shows when truncating

Components

• BreadcrumbsRoot - context provider, manages visibility
• BreadcrumbsList - semantic ol wrapper
• BreadcrumbsItem - breadcrumb link/text
• BreadcrumbsDivider - separator with inline override support
• BreadcrumbsEllipsis - truncation indicator

Usage

<Breadcrumbs.Root divider="/" as="nav">
  <Breadcrumbs.List as="ol">
    <Breadcrumbs.Item as="li"><a href="/">Home</a></Breadcrumbs.Item>
    <Breadcrumbs.Divider />
    <Breadcrumbs.Ellipsis />
    <Breadcrumbs.Divider />
    <Breadcrumbs.Item as="li"><a href="/about">About</a></Breadcrumbs.Item>
  </Breadcrumbs.List>
</Breadcrumbs.Root>

Test plan

• Manual testing in playground
• Add unit tests for Breadcrumbs components
• Test overflow behavior at various widths
• Verify ellipsis visibility logic

[pkg-pr-new]

Open in StackBlitz

commit: a46ad9f