mcp: remove the restart/kill/start/update/get_logs agent verbs

Container lifecycle from inside an agent goes away: an agent no longer
starts, stops, restarts or rebuilds a container in its subtree, and no
longer reads another container's journal. Those are operator actions —
the dashboard and hivectl keep their own paths to the same job-queue
and hive-priv plumbing, which is why none of that machinery is removed
here, only the five MCP verbs and what they alone reached.

What went with them: the `Request` variants and `Response::Logs` on the
agent socket, the five tool definitions and their arg structs, the four
lifecycle handlers plus `handle_get_logs`, and `require_descendant` —
the topology guard those five were the only remaining callers of.
`ToolGroup::Diagnostics` goes too: `get_logs` was its only tool, so it
would otherwise be a grantable group that grants nothing. `lifecycle`
stays, now carrying `list_containers` alone.

An agent that gets a `needs_update` or `container_crash` helper event
has no remedy of its own left, so the system prompt and the docs now
send it to the operator instead of to a tool that no longer exists.

Refs #4480

hive-c0re/src/dashboard/lifecycle_ops.rs

@@ -107,10 +107,7 @@ pub(super) async fn post_kill(
     // submitted by other sub-agents still process through the
     // host-side approval queue without the manager up, and
     // operator-driven meta-input updates work from the dashboard
-    // either way. The MCP-surface self-kill guard in
-    // `socket_server.rs::Request::Kill` stays in place: a
-    // manager calling Kill on its own container is self-suicide
-    // mid-call, not a legitimate operator action.
+    // either way.
     if let Err(e) =
         crate::job_queue::power::stop_many(&state.coord, std::slice::from_ref(&logical), false)
             .await