Draw a plan's order per module from the graph and the manifests' change, and read no after: line (issue 977, part B, ADR 0419)

internal/inventory/plans.go

@@ -292,6 +292,9 @@ type PlanModule struct {
 	FirstAt *time.Time `json:"first_at,omitempty"`
 	Commit  string     `json:"commit,omitempty"`
 	Why     string     `json:"why,omitempty"`
+	// Placed is the edge that put the module after another, and the rule that drew it (novox/hq ADR 0419 clause 5):
+	// "after <module> (verb before caller: <seat>.<verb>)". Empty for a module placed first by nothing.
+	Placed string `json:"placed,omitempty"`
 	// Made is what the walk's build of it did (novox/hq ADR 0350 §4): "reused from <check build>", naming the pull
 	// request's head, the trunk commit and the digests, or "built: <why>". Said in `plan-moved` and kept here.
 	Made string `json:"made,omitempty"`