feat(react-nav): add useNavBase_unstable hook

[dmytrokirpa]

Stack

This PR is part of a 3-PR stack. Review and merge bottom-up:

1. test(react-nav): add hook-level regression tests for react-nav components #36212 — test(react-nav): hook-level regression tests (base: master) — merge first
2. 👉 feat(react-nav): add useNavBase_unstable hook #35812 — feat(react-nav): expose base hooks (base: test(react-nav): add hook-level regression tests for react-nav components #36212) — depends on test(react-nav): add hook-level regression tests for react-nav components #36212
3. feat(react-headless-components-preview): add Nav component and stories #36213 — feat(react-headless-components-preview): add Nav component (base: feat(react-nav): add useNavBase_unstable hook #35812) — depends on this PR

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Summary

• Adds useNavBase_unstable hook to react-nav that extracts pure Nav logic (selection state, category toggling, nav item registration) without the density design prop
• Adds useNavCategoryBase_unstable hook for NavCategory (manages open/closed state from context) — no design props to omit, mirrors existing hook
• Adds useNavCategoryItemBase_unstable hook for NavCategoryItem that excludes the density design prop while preserving ARIA attributes (aria-current, aria-expanded) and keyboard event handling
• Adds corresponding NavBaseProps, NavBaseState, NavCategoryBaseProps, NavCategoryBaseState, NavCategoryItemBaseProps, NavCategoryItemBaseState types using DistributiveOmit
• Refactors useNav_unstable and useNavCategoryItem_unstable to delegate to their base hooks, then add design props
• Exports all new types and hooks from the package index.ts

Design props excluded

Component	Omitted props
Nav	density
NavCategory	(none — no design props)
NavCategoryItem	density

Test plan

• TypeScript compiles without errors (npx tsc -p packages/react-components/react-nav/library/tsconfig.json --noEmit)
• Existing Nav functionality is unchanged (base hooks delegate correctly)
• New hooks are exported from the package index

🤖 Generated with Claude Code

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Pull request demo site: URL

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📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
react-components react-components: entire library	1.294 MB 325.186 kB	1.294 MB 325.274 kB	435 B 88 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-components react-components: Button, FluentProvider & webLightTheme	67.61 kB 19.536 kB
react-components react-components: Accordion, Button, FluentProvider, Image, Menu, Popover	227.925 kB 68.478 kB
react-components react-components: FluentProvider & webLightTheme	40.806 kB 13.616 kB
react-portal-compat PortalCompatProvider	5.567 kB 2.237 kB
react-timepicker-compat TimePicker	105.613 kB 35.351 kB

_{🤖 This report was generated against 7d754a92091660adf575d533e3f7c6d3224ec81a}