Configure devcontainer to persist VS Code settings and Kilo Code state across container rebuilds by adding dedicated volume mounts for:
- Global storage (threads, caches, extensions)
- User settings
Also added workspaceMount and workspaceFolder configuration for better workspace management.
Includes documentation for devcontainer persistence setup.
Updated core concepts section with new entries and descriptions, including Provider, Foundational Models, Prompt Engineering, Modes, Codebase Indexing, and MCP. Removed outdated concepts and added relevant video previews.