Restore Tab/Shift+Tab focus-exit test coverage #3122

Context

PR #3121 migrated unit tests from Playwright to Puppeteer. Puppeteer cannot move focus outside the browser viewport via Tab/Shift+Tab, so four assertions that verified focus leaving a component were removed or weakened.

Removed/weakened assertions

1. Accordion: Shift+Tab from first header exits accordion - removed entirely (no prior focusable element to land on)
2. Accordion: Shift+Tab from last header exits accordion - removed entirely
3. Accordion: Tab out then Shift+Tab back returns to panel link - removed the Shift+Tab return portion
4. Search-input: Tab from expanded listbox defocuses combobox - changed from asserting nothing is focused to asserting listbox is closed

What to restore

All four cases test that focus leaves the component entirely via Tab/Shift+Tab. Options:

• Add Playwright e2e tests (*.e2e.ts) for these keyboard navigation flows, since e2e tests still run on Playwright
• Investigate whether Puppeteer's page.bringToFront() or CDP Input.dispatchKeyEvent with proper target can simulate Tab-out behavior
• Use a sentinel focusable element before/after the component in the test fixture to catch focus without needing to leave the page

Files affected

• elements/pf-v5-accordion/test/pf-accordion.spec.ts
• elements/pf-v5-search-input/test/pf-search-input.spec.ts