Docker Sandboxes: Declarative sbxenv.yaml Environments Overview (schemaVersion , EXPERIMENTAL) declaratively describes one sandbox environment — agent, mixin kits, workspace mounts, environment variables, secrets/registries/bindings to provision, MCP servers, ports, and host-side lifecycle commands — so can stand it up and tear it down reproducibly instead of a long flag invocation. This skill owns that file format end to end. It delegates the sandbox lifecycle semantics it wraps, the credential/network model it provisions into, and the kit schema its entries reference, to their own skills. W…