[SelectPanel] Announce loading prop changes

[hectahertz]

Closes https://github.com/github/primer/issues/4978

Changelog

This pull request introduces a new useEffect hook in the SelectPanel component to manage loading announcements when loading is managed via props.

The change also ensures a smooth user experience by delaying announcements for quick-loading scenarios.

New

Added logic to handle announcements when the loading prop changes

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 (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: 56779a3

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	Patch

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[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github depends on. If you are GitHub staff, we recommend testing these changes with github/github using the integration workflow. Thanks!

[Copilot]

Pull Request Overview

This PR adds accessibility improvements to the SelectPanel component by implementing loading state announcements when loading is managed externally via props. The change ensures screen reader users are informed when content is loading, with a delay mechanism to avoid unnecessary announcements for quick operations.

• Adds a new useEffect hook to handle loading announcements when loadingManagedExternally is true
• Implements delayed announcement logic to prevent announcing loading for quick operations
• Provides proper cleanup of loading announcements when loading completes

[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	92.36 KB (+0.06% 🔺)
packages/react/dist/browser.umd.js	92.47 KB (0%)