Invocation Mode overview

Selects where a harness subprocess runs. adapters defines four modes — local (default), docker (`docker run --rm -i ...`), ssh (`ssh ... -- 'cd <cwd> && cmd ...'`), and k8s (`kubectl exec -i <pod> -- ...`). The adapter contract emits a mode-agnostic SpawnArgs which a pure transform rewrites for the chosen host. Source: docs/adapters/reference/13-invocation-modes.md.