Send an approved settings layer by a walk at once, so the operator's Approve is the act that takes effect (issue 641, ADR 0344)

The warrant set the layer and left the push as a second act nobody took: the
operator approved a betterbird change on Telegram and nothing reached g14.
Now the warrant opens a settings walk: the machines the layer reaches, one at
a time, the module judged on each at its gate, its end told once through
plan-moved. The ask and the proposer's answer say so instead of naming push.

internal/inventory/plans.go

@@ -433,6 +433,20 @@ type PlanRelease struct {
 	Skipped []string `json:"skipped,omitempty"`
 	// By is the person who released it, empty when the mesh did.
 	By string `json:"by,omitempty"`
+	// Settings is set on a settings walk (novox/hq ADR 0344): not the builds waiting for a gate, but a settings
+	// layer the operator approved, sent to the machines it reaches one at a time, its module judged on each.
+	Settings *PlanSettings `json:"settings,omitempty"`
+}
+
+// PlanSettings is what a settings walk sends (novox/hq ADR 0344): the module whose layer the operator approved, the
+// layer's scope, the ask that approved it and what changed, in words.
+type PlanSettings struct {
+	Module string `json:"module"`
+	// Node is the machine the layer is for, empty for the whole mesh.
+	Node string `json:"node,omitempty"`
+	// Ask is the proposal the operator approved, and Change what its layer changed ("~ prefs").
+	Ask    string `json:"ask"`
+	Change string `json:"change,omitempty"`
 }
 
 // The states a plan passes through.