On your closing question about whether mode plus typed confirmation plus human approval is the right default: I think the split is right, and the layers are not doing equal work, so it is worth being explicit about which one carries which failure.
Typed confirmation and elicitation defend against different things, and only one of them survives the case you built this for. The confirm value is produced by the model, so it catches a model being careless about a destructive call and does nothing about a model that is confident and wrong about which cluster it is pointed at. You say as much in the update. Elicitation is the layer that actually binds, which makes the interesting question not whether to keep the others but which operations are allowed to skip elicitation, and that list is worth writing down directly rather than deriving it from ALLOW_DELETE.
The gap I would look at hardest is that all eight layers sit on the write path, and read-only is both the mode most people will run and the way an attacker gets in. Reading pod logs out of kube-system, or a Grafana annotation, or a row from ClickHouse pulls text somebody else wrote into the context that decides the next tool call. A read-only Kubernetes server and a read-write anything server in the same session compose into a write-capable system, and the policy engine cannot see that, because it is scoped per server. Whatever the composition story is, I would put it in the docs, because the safe default of one server is not the safe default of the set.
On the mode itself: K8S_MODE is read at process start, so the blast radius is the session rather than the call. The incident shape I have cleaned up more than once is someone starting a tool in write mode for one task on a Tuesday and it still being in write mode on Friday. A mode that decays back to read-only after a fixed window, or after one successful write, removes that without changing the interface much.
Last one, and it is the one I would fix first because it is cheap. Audit lines on stderr under stdio land in the client's log file on somebody's laptop, which is exactly where they are not when you need them. Every guarded op wants a correlation ID tying the call back to the conversation turn that asked for it, shipped somewhere the agent host does not own. At 2am the question is never what the server did. It is who asked it to, and why it was allowed.
