Give each node a bucket of its own for the files that travel by digest, and keep the sweep from removing an object a send relies on (issues 1696, 1697; review of ADR 0486 step 3)

A literal * in a published subject matches the grant's *, so in one shared bucket a node could read every node's files. Each node now
has declaration-files-<node>, which its account reads by name and the controller writes; the sweep judges each bucket against that
node's latest declaration, under the node's lock with the send, and an object the sweep marked is put again by the next send. Putting
that fails send after send raises a condition.

cmd/mesh-controller/plain_words.go

@@ -195,6 +195,14 @@ var plainWordings = map[string]func(conditions.Observation) words{
 				"there yet is sealed by the controller until the vault holds it.", m, m),
 			Resolved: "Resolved: the vault gave " + m + " the core's credentials"}
 	}),
+	kindFilesNotPut: worded(func(o conditions.Observation) words {
+		m := machineOr(o, "a machine")
+		return words{Headline: "The big files for " + m + " cannot be put on the bus",
+			Needs: "look at the bus's permissions for the controller; the details give the reason.",
+			Explanation: fmt.Sprintf("The mesh could not put the large files of %s's instructions in their place on the bus, "+
+				"send after send, so %s is sent them inside the instructions instead, which may make them too big.", m, m),
+			Resolved: "Resolved: the big files for " + m + " reach the bus again"}
+	}),
 	kindDeclarationNearLimit: worded(func(o conditions.Observation) words {
 		m := machineOr(o, "a machine")
 		if o.Severity == conditions.Urgent {