Migrate batch of components from Jest to Vitest

[Copilot]

This PR migrates a batch of components from Jest to Vitest testing framework as part of the ongoing migration effort.

Components Migrated

• ✅ Link - Migrated successfully (8 tests passing)
• ✅ Popover - Migrated successfully (14 tests passing)
• ✅ Header - Migrated successfully (6 tests passing)
• ✅ UnderlineNav - Already migrated (7 tests passing)
• ✅ Hidden - Already migrated (3 tests passing, snapshot updated)

Changes Made

Configuration Updates

• Added Link, Popover, and Header to vitest.config.browser.mts include patterns
• Added Link, Popover, and Header to jest.config.js modulePathIgnorePatterns

Test File Migrations

• Updated imports from Jest to Vitest (describe, expect, it, vi)
• Replaced render from utils/testing with @testing-library/react
• Removed behavesAsComponent usage (replaced with direct component tests)
• Removed checkExports usage (no longer needed in Vitest migration)
• Removed axe accessibility tests with toHaveNoViolations
• Replaced snapshot-based tests with actual DOM assertions for better reliability
• Fixed console spy usage for browser environment (globalThis.console instead of global.console)

Test Improvements

• Link tests now properly assert on DOM attributes and styles instead of snapshots
• Popover tests verify caret positioning through data attributes
• Header tests check actual DOM structure and accessibility attributes
• Updated Hidden component snapshot due to CSS module hash changes

All 38 tests across the 5 components are now passing with Vitest! 🎉

Fixes #6355.

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[changeset-bot]

⚠️ No Changeset found

Latest commit: c325650

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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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!

[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	91.96 KB (0%)
packages/react/dist/browser.umd.js	92.21 KB (0%)