TreeView: add as prop to TreeView.Item

[liuliu-dev]

Closes https://github.com/github/primer/issues/6495 and closes https://github.com/github/core-ux/issues/2495

Adds support for the as prop on TreeView.Item, enabling consumers to render the tree item as a different element (e.g. a native <a> or a custom router-link component) while preserving all existing keyboard, focus, and ARIA behavior. This brings TreeView.Item in line with other polymorphic Primer components such as Breadcrumbs.Item and ActionList.LinkItem.

// Native anchor
<TreeView.Item id="overview" as="a" href="/overview">Overview</TreeView.Item>

// Custom router link
<TreeView.Item id="docs" as={RouterLink} to="/docs">Docs</TreeView.Item>

Changelog

New

Changed

Removed

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; if selected, include a brief description as to why

Testing & Reviewing

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge
• (GitHub staff only) Integration tests pass at github/github-ui (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: 81d647b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

⚠️ Action required

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Check the integration testing docs for step-by-step instructions. Or, apply the integration-tests: skipped manually label to skip these checks.

To publish a canary release for integration testing, apply the Canary Release label to this PR.

[primer-integration]

👋 Hi from github/github-ui! Your integration PR is ready: https://github.com/github/github-ui/pull/21835

[primer-integration]

Integration test results from github/github-ui:

  CI Passed
  VRT Passed
  Projects Passed

All checks passed!