Support for Claude Code

[aboo]

Problem

At the moment we do not support Claude Code. The only supported harness is OpenCode.

Proposed solution

• Add support for Claude Code by converting and adapting the current agents, commands and harness configs
• Add a step to workbench setup to toggle which harness to add (multiple selection should be allowed) — the list will grow in the future with other harnesses
• cli - Add ability to add a harness config midway for example workbench --add-harness claude-code
• cli - Add ability to remove harness config midway for example workbench --remove-harness opencode

Additional context

This repo converts from opencode to claude code. We could potentially get inspired from:
https://github.com/enulus/OpenPackage

[Keesan12]

One thing I would make explicit in the harness abstraction is which state is harness-specific versus runtime-specific. The easy part is command and config conversion; the expensive part later is discovering that retries, stop reasons, approvals, and receipts mean slightly different things across harnesses. I would strongly recommend defining a canonical attempt contract first, then adapting Claude Code and OpenCode into that shape. That is the boundary we ended up caring about in MartinLoop. If you want to compare notes against a concrete OSS shape while you wire support in, happy to.