Name the account agents run as on a node, and say whether it can become root

On the control node every agent ran as the operator's account, which has
passwordless sudo, so an agent could become root without a person (hq ADR
0266). A node now names an agent account at the controller's terminal only;
the agent's module declares it never to become root, the node-engine judges
that, and the self-check (DA) raises agent-can-become-root while it does not
hold, so ADR 0259's router can rest on it.

internal/catalogue/resolve.go

@@ -32,6 +32,11 @@ type Node struct {
 	// to-be 29). What a home-scoped file is owned by and what ${machine:account} resolves to.
 	Account     string
 	AccountHome string
+	// AgentAccount is the login agents run as here when it is not the operator's, AgentAccountHome its
+	// home when not derived (novox/hq ADR 0266). What ${machine:agent-account} resolves to; empty means
+	// agents run as the operator account.
+	AgentAccount     string
+	AgentAccountHome string
 }
 
 // World is what the rest of the mesh already has.
@@ -134,6 +139,10 @@ type Resolution struct {
 	// here without a store lookup.
 	Account     string
 	AccountHome string
+	// AgentAccount and AgentAccountHome are the account agents run as here when it is not the
+	// operator's, and its home (novox/hq ADR 0266); empty when agents run as the operator account.
+	AgentAccount     string
+	AgentAccountHome string
 	// Capabilities are the machine's, as its profile reported them, carried from the node so a
 	// contribution placed only where the machine has something (`if-capability`, novox/hq ADR 0255)
 	// is decided here without a store lookup.
@@ -703,7 +712,8 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 	}
 
 	resolution := Resolution{Node: node.Name, At: node.At, PublicDomain: node.PublicDomain,
-		Account: node.Account, AccountHome: node.AccountHome, Capabilities: node.Capabilities,
+		Account: node.Account, AccountHome: node.AccountHome, AgentAccount: node.AgentAccount,
+		AgentAccountHome: node.AgentAccountHome, Capabilities: node.Capabilities,
 		Because: because, Needs: needs, Unhostable: unhostable, Kept: kept}
 	for _, n := range providersFirst(order, catalogue) {
 		resolution.Modules = append(resolution.Modules, catalogue[n])