[feature] MCP passthrough mode in v2 #2198

The problem

My harness already has codemode, and I dont want to do codemode-thru-codemode

Proposed shape

I want a mode that works similarly to v1's passthrough, where app supplied sub-tools (including executor app ones) are exposed directly as mcp server tools

Alternatives

No response

Where it belongs

Executor Cloud, CLI, Desktop app, Self-host (Docker), Self-host (Cloudflare)

Before you submit

• I searched the open issues for a duplicate.