[FEATURE] Context File Preloading and Custom Agent Configuration

Preflight Checklist

• I have searched existing requests and this feature hasn't been requested yet
• This is a single feature request

Feature Request

Add support for context file preloading and custom agent configurations, similar to the comprehensive system proposed for GitHub Copilot CLI.

Problem

Currently, Claude Code requires manual context provision for each session. Users working on complex projects must repeatedly provide the same contextual information (project structure, coding standards, documentation) in every new conversation.

Proposed Solution

Implement a configuration system that allows users to:

• Define custom agents with pre-loaded context from specified files and patterns
• Set agent-specific prompts and behavior
• Automatically load project documentation, configuration files, and relevant code
• Create project-specific and global agent configurations

Reference Implementation

See the detailed specification and use cases in GitHub Copilot CLI Issue #62, which provides a comprehensive design for this exact functionality.

Benefits

• Eliminates repetitive context setup
• Enables domain-specific assistance (AWS, Kubernetes, etc.)
• Improves onboarding for new team members
• Supports organizational knowledge sharing

Example Use Case

{
  "name": "project-assistant",
  "prompt": "You are familiar with this project's architecture and coding standards",
  "resources": [
    "file://README.md",
    "file://docs/**/*.md",
    "file://**/*.config.js"
  ]
}

This would position Claude Code competitively with other AI coding assistants implementing similar context management features.