Add navigation menu component from Base UI

[devin-ai-integration]

Enhanced Navigation Menu Demo to Match Base UI Example

Summary

This PR enhances the navigation menu component implementation to more closely match the Base UI documentation example. The changes include:

• Added missing props to NavigationMenuRoot component (delay, close_delay, actions_ref, on_open_change_complete)
• Updated component descriptions to match Base UI documentation exactly for all sub-components
• Created comprehensive demo with Overview and Handbook dropdowns containing rich content (titles, descriptions, links)
• Enhanced styling with better transitions, hover states, and visual feedback
• Fixed syntax error by changing rx.html to rx.el for HTML elements

The demo now showcases a realistic navigation menu with:

• Overview dropdown: Quick Start, Accessibility, Releases (2-column grid layout)
• Handbook dropdown: Styling, Animation (single column layout)
• GitHub direct link: No dropdown, direct navigation

Review & Testing Checklist for Human

• Visual positioning of dropdowns: Verify dropdown menus appear correctly positioned and sized when hovering/clicking Overview and Handbook buttons
• Interactive functionality: Test all click handlers work correctly (Overview links, Handbook links, GitHub link) and show proper toast notifications
• Styling accuracy: Compare dropdown appearance with Base UI example to ensure visual consistency and proper styling
• Console error checking: Verify no JavaScript errors appear in browser console during navigation menu interactions
• Accessibility testing: Test keyboard navigation (Tab, Enter, Escape) and screen reader compatibility

Recommended test plan: Run uv run reflex run in the demo directory, navigate to localhost:3000, and thoroughly test all navigation menu interactions including hover states, click handlers, and visual appearance.

---

Diagram

%%{ init : { "theme" : "default" }}%%
graph TD
    A["reflex_ui/components/base/navigation_menu.py<br/>NavigationMenu Implementation"]:::major-edit
    B["demo/demo/demo.py<br/>Demo Application"]:::major-edit
    C["reflex_ui/__init__.py<br/>Component Registry"]:::context
    D["Base UI Documentation<br/>@base-ui-components/react"]:::context
    
    A --> B
    C --> A
    D --> A
    
    A --> E["NavigationMenuRoot<br/>Added missing props"]:::minor-edit
    A --> F["Component Descriptions<br/>Updated to match Base UI"]:::minor-edit
    A --> G["ClassNames<br/>Enhanced styling"]:::minor-edit
    
    B --> H["Overview Dropdown<br/>Quick Start, Accessibility, Releases"]:::major-edit
    B --> I["Handbook Dropdown<br/>Styling, Animation"]:::major-edit
    B --> J["GitHub Link<br/>Direct navigation"]:::major-edit
    
    subgraph Legend
        L1[Major Edit]:::major-edit
        L2[Minor Edit]:::minor-edit
        L3[Context/No Edit]:::context
    end
    
    classDef major-edit fill:#90EE90
    classDef minor-edit fill:#87CEEB
    classDef context fill:#FFFFFF

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Notes

• The dropdown content showed as "offscreen" in HTML during testing, which may indicate positioning issues that need visual verification
• All pre-commit checks passed (ruff, codespell, pyright)
• This implementation maintains the existing granular API structure without adding a high-level component (per user request)
• Session URL: https://app.devin.ai/sessions/013efce6ad5445ef9f2e759a8a698c57
• Requested by: Carlos Cutillas (carlos@reflex.dev)

[devin-ai-integration]

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