Fix breadcrumbs

[danielguillan]

Fixes the issue of duplicate items on index pages and adds tabbed navigation labels to breadcrumbs.

Before	After

[Copilot]

Pull Request Overview

Fix duplicate breadcrumb entries and add tab-based labels to navigation.

• Filters out redundant index pages in the breadcrumb trail
• Uses frontMatter tab-label for titles and updates the last-item selection logic
• Adds a changeset entry for the patch release

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
packages/theme/components/layout/root-layout/Theme.tsx	Refactor breadcrumb rendering: filter duplicates, apply tab-label, and update selected
.changeset/cool-cows-shake.md	Add patch changeset describing the breadcrumb fix

Comments suppressed due to low confidence (1)

packages/theme/components/layout/root-layout/Theme.tsx:153

• Add unit tests covering scenarios for folder-index collisions and tab-label filtering to ensure the breadcrumb logic behaves as expected.

                                  .filter((item, index, array) => {

[danielguillan]

I'm not sure how to avoid disabling the linter here, the fontMatter check is actually necessary.

[rezrah]

Is checking for frontMatter required? I thought it was always available through Nextra, but empty if nothing was added there? If that's the case you could remove it the optional chain. Or are you trying to check if tab-label is available on the frontMatter object?

[rezrah]

If frontMatter is optional, we need to adjust the types in types.ts to reflect that. But that will likely lead to a bigger job so in that case, let's leave as-is and mop up later.

[rezrah]

This is looking great Dani.