db857f62c0
The sandbox docs overclaimed a containment contract the design never makes: "capability access is routed through cordis services, never Node built-ins, so everything a mounted plugin does stays inspectable and disposable". The host-realm helpers on the sandbox global (harness, console, btoa) are reachable functions, so mount code that goes looking can reach the host realm through one of them — accepted under the trust stance, because the ctx a mount ultimately receives is fully privileged anyway. Reword the sandbox module doc, the README trust stance, and the RFC sandbox-semantics section to say exactly that: the traps and small global surface STEER honest code onto the cordis services; they are not a security boundary.