feat: add system builder and reorganize project structure

New Features:
- Add system-builder agent for generating custom AI systems
- Add 5 new subagents for system building:
  - domain-analyzer: Analyzes domains and recommends architectures
  - agent-generator: Generates XML-optimized agent files
  - context-organizer: Organizes modular context files
  - workflow-designer: Designs workflow definitions
  - command-creator: Creates custom slash commands
- Add build-context-system command for interactive system generation
- Add system builder templates and guide

Project Reorganization:
- Move GITHUB_SETTINGS.md to docs/github/
- Move AGENT-SYSTEM-BLUEPRINT.md to docs/features/
- Move CODE_OF_CONDUCT.md to docs/contributing/
- Move CONTRIBUTING.md to docs/contributing/
- Consolidate documentation in docs/ directory

Registry Updates:
- Add system-builder agent to registry
- Add 5 new subagents to registry
- Add build-context-system command to registry
- Update advanced profile to include system builder components

This enables users to generate complete custom AI systems tailored to their domain through an interactive interview process.