Add subagent support

[cmungall]

Claude has subagents, goose has them too (but experimental)

Currently if you want to use subagents you need to use tool-specific conf files. We can come up with a common model (based on A2A... or just use the claude frontmatter style which is nice) and compile down, but not supported yet

[dragon-ai-agent]

Status Update on Subagent Support

I examined the current codebase for subagent implementation:

Current Status:

• The Claude coder has a TODO comment: "TODO: support sub-agents"
• There is infrastructure in place: .claude/agents directory is mapped to ConfigFileRole.AGENTS
• No actual subagent implementation is present yet

Technical Requirements:
To implement this feature, we need to:

1. Define Common Subagent Model: Create a standardized YAML/JSON format for defining subagents across all coders
2. Claude Integration: Implement Claude frontmatter-style subagent configuration compilation
3. Goose Integration: Add support for Goose experimental subagent features
4. Configuration Compilation: Add logic to convert the common format to tool-specific configs

Suggested Implementation Plan:

1. Research current Claude and Goose subagent configuration formats
2. Design a unified metacoder subagent YAML schema
3. Implement compilation logic for each coder
4. Add command-line options for specifying subagents (e.g., --subagent my-agent)

Status: Ready for implementation - requires design decisions on the common configuration format.

Would you like me to research the specific subagent formats used by Claude and Goose to propose a unified schema?