The pack does not run itself, so something has to. That something is any capable agent, and this is the pack's core claim: the agent is the runtime and the pack is only the bill of materials it reads from. Integration is one instruction. Point an agent at the checkout, tell it to read skills/delegate/SKILL.md and follow it, and it resolves every named skill and role prompt from the same tree.
Harness-agnostic is not the same as capability-free. A full run still needs filesystem access, shell execution, Git worktrees, and worker and reviewer subagents, with gh on top for pull-request integration. Where a harness has no notion of named roles, it simply hands the Markdown role prompt to a generic subagent instead. The point of moving execution out of the pack and into the agent is that the same law runs under different tools rather than being rewritten for each one.