Add prominent archive notices and documentation

Co-authored-by: pacnpal <183241239+pacnpal@users.noreply.github.com>

ARCHIVE_NOTICE.md

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+# Archive Notice
+
+## Repository Status
+
+**This repository has been archived and is now read-only.**
+
+- **Archive Date**: January 31, 2026
+- **Last Active Maintenance**: 2025
+- **Status**: No longer maintained or supported
+
+## Why Was This Repository Archived?
+
+This project has been archived for the following reasons:
+
+1. **Official Alternatives Available**: Anthropic now provides official integrations and tools for Claude AI that are more robust and better maintained.
+
+2. **Better Solutions Exist**: The AI code review ecosystem has matured significantly, with enterprise-grade solutions available that offer more features and better support.
+
+3. **Maintenance Burden**: As a community project, maintaining compatibility with rapidly evolving AI APIs and GitHub Actions became unsustainable.
+
+## What Does "Archived" Mean?
+
+An archived repository is read-only, which means:
+
+- ✅ The code remains accessible for reference and historical purposes
+- ✅ You can still clone and fork the repository
+- ✅ Existing workflows using this action will continue to work (until API changes break them)
+- ❌ No new issues can be opened
+- ❌ No new pull requests can be submitted
+- ❌ No updates or bug fixes will be provided
+- ❌ No support or maintenance will be available
+
+## Recommended Alternatives
+
+We recommend migrating to one of these alternatives:
+
+### 1. **Anthropic API Direct Integration**
+- Use the official [Anthropic API](https://docs.anthropic.com/) with the latest Claude models
+- Full control and customization
+- Best for teams with development resources
+
+### 2. **GitHub Copilot**
+- Native GitHub integration
+- Real-time code assistance
+- Note: Uses primarily OpenAI models, not Claude
+
+### 3. **Third-Party AI Code Review Tools**
+- Many SaaS solutions now offer AI-powered code review
+- Check the GitHub Marketplace for current options
+- Look for solutions with active maintenance and support
+
+### 4. **Claude for Workspace**
+- Enterprise-level integration
+- Designed for team workflows
+- Contact Anthropic for availability
+
+## Migration Guide
+
+If you're currently using this action and need to migrate:
+
+1. **Assess Your Needs**
+   - Determine what features you rely on
+   - Evaluate whether you need automated reviews or manual AI assistance
+
+2. **Choose an Alternative**
+   - Research current solutions (see recommendations above)
+   - Consider your budget and team size
+   - Evaluate security and privacy requirements
+
+3. **Update Your Workflows**
+   - Remove or comment out this action from your `.github/workflows/` files
+   - Replace with your chosen alternative
+   - Test thoroughly in a non-production environment first
+
+4. **Remove the Action**
+   - Once migrated, remove the workflow file or action reference
+   - Clean up any related secrets (keep them if migrating to Anthropic API)
+
+## For Historical Reference
+
+This repository will remain available indefinitely for:
+- Historical reference
+- Learning from the implementation
+- Forking for custom solutions
+- Understanding the deprecated API patterns
+
+## Contact
+
+For questions about this archive:
+- **Repository Owner**: PacNPal
+- **Archive Reason**: Project deprecated in favor of official solutions
+- **Historical Issues**: Available in the Issues tab (read-only)
+
+## License
+
+This project remains under the MIT License. You may fork and modify it for your own use, but please note:
+- No support will be provided
+- APIs may have changed since archival
+- Security vulnerabilities will not be patched
+
+---
+
+**Thank you to all contributors and users who made this project successful during its active development!**
+
+*Last Updated: January 31, 2026*