Name the node-engine's data items state, so mesh-host writes and disk-load reads one shape (ADR 0577)

The contract (state name, key form, value) is in delivery; buscompose grants the engine its own
node's keys of mesh-host_data and each node's disk-load a read of its own node's keys alone, the
same way the engine's other states are granted.

Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL

go/buscompose/engine.go

@@ -28,6 +28,10 @@ var EngineActsBucket = BucketName(EngineModule, EngineActsState)
 // node's name, written by that node's engine alone.
 var EnginePackagesBucket = BucketName(EngineModule, delivery.EnginePackagesState)
 
+// EngineDataBucket is the engine's state of its node's placed modules' data items (novox/hq ADR 0577 clause 1): one
+// key `<node>.<module>` per module, written by that node's engine alone.
+var EngineDataBucket = delivery.EngineDataBucket
+
 // EnginePackagesGrants is what a node's engine publishes to keep its node's key of the packages bucket: the key alone,
 // and its read.
 func EnginePackagesGrants(node string) []string {
@@ -66,6 +70,10 @@ func engineGrants(p Principal) (pub, sub []string) {
 		pub = append(pub, append([]string{"$KV." + delivery.NodeHealthBucket + "." + p.Node},
 			readGrants(delivery.NodeHealthBucket, p.Node)...)...)
 	}
+	// And its node's placed modules' data items, its own node's keys alone (ADR 0577 clause 1).
+	if own, err := NodeKeysGrants(EngineDataBucket, p.Node); err == nil {
+		pub = append(pub, own...)
+	}
 	// And its node's declared packages, its own key alone (ADR 0565 clause 6).
 	if safeSubject.MatchString(p.Node) {
 		pub = append(pub, EnginePackagesGrants(p.Node)...)