Add Next.js front-end specialist agent mode

[kristiyan-velkov]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• My contribution adds a new instruction, prompt, or chat mode file in the correct directory.
• The file follows the required naming convention.
• The content is clearly structured and follows the example format.
• I have tested my instructions, prompt, or chat mode with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.

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Description

This PR adds a comprehensive Next.js Front-End Specialist chat mode designed for developers building production-ready applications using modern front-end technologies and best practices.

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Type of Contribution

• New chat mode file.

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Additional Notes

Key Features:

• Next.js App Router with file-based routing, layouts, templates, and route groups
• Server and Client Components with use cache directive for Partial Prerendering (PPR)
• Turbopack bundler (now stable) with filesystem caching for faster builds
• React Compiler Integration for automatic memoization and optimization
• Advanced Data Fetching using Server Components, caching strategies, streaming, and suspense
• TypeScript Integration for async params, metadata, and API routes
• Performance Optimization including image and font optimization, lazy loading, and code splitting
• Routing Patterns with dynamic routes, intercepting routes, parallel routes, and route groups
• Metadata & SEO using Next.js Metadata API with Open Graph and Twitter cards
• Accessibility & Progressive Enhancement following WCAG and modern UX best practices
• Middleware & Authentication with route protection and session management
• Deployment Ready for Vercel, Docker, or self-hosted environments

This chat mode is particularly useful for teams building modern Next.js 16 applications that demand performance, scalability, type safety, and design system consistency while adhering to the latest React Server Components architecture.

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By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.