Revamps AI documentation and removes beta warnings

[brianlagunas]

• Restructures AI documentation:
  • Organizes AI topics into new "Using the SDK", "API Reference", and "Guides" categories.
  • Separates client-side SDK usage and common patterns (streaming, error handling, chat interface, context menus) into dedicated guides.
  • Renames existing API docs (e.g., chat.md to Chat Endpoint) to focus on server-side endpoint details.
• Removes beta warnings:
  • Eliminates "Product in Beta" banners across all AI documentation files, indicating feature maturity.
• Updates client-side examples:
  • Simplifies the HTML/JavaScript Getting Started guide, providing a more focused initial experience.
  • Refactors streaming code examples in the overview.
• Refines metadata catalog configuration:
  • Clarifies how to configure the metadata catalog from external JSON files and custom providers.
• Improves internal navigation:
  • Updates homepage links and Docusaurus sidebar to reflect the new doc structure and use native `` components.
• Updates translations:
  • Applies all content and structural changes to Japanese localized documentation, including fixes for previous issues.
• Enhances internal tooling:
  • Adds Docusaurus clear command and directory listing to local Claude settings for improved documentation generation.