fix(react-headless-components-preview): use tab navigation in Nav instead of arrow keys

[Dmytro Kirpa (dmytrokirpa)]

Description

Removes the focusgroup arrow-key navigation from Nav and NavDrawerBody in the headless preview package. Navigation items are now reachable with sequential Tab navigation.

• useNav no longer sets focusgroup="toolbar block wrap"; it still sets role="navigation".
• useNavDrawerBody no longer sets focusgroup; it still sets role="navigation".
• Dropped Nav from the focusgroup browser-support notice in the stories.

Nav links are natively focusable, so tab navigation matches the expected behavior of a list of links and removes the dependency on the focusgroup polyfill for this component. The navigation landmark role is preserved on both surfaces.

Verification

yarn nx run react-headless-components-preview:test -t Nav passes.

[github-actions]

Pull request demo site: URL

[github-actions]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
react-headless-components-preview react-headless-components-preview: entire library	238.059 kB 67.025 kB	237.981 kB 67.017 kB	-78 B -8 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-headless-components-preview @fluentui/react-headless-components-preview/tag-picker	53.982 kB 17.74 kB
react-headless-components-preview @fluentui/react-headless-components-preview/teaching-popover	36.041 kB 11.992 kB

_{🤖 This report was generated against b5ec47fc035849b21b35d6f6054d60c0a64ff3db}