Let the tree readers decode, give the judge the manifest's data it reads, and stop judging outside the catalogue (ADR 0578 §3, §4)

Issue 1585, S6-S8: ReadTreeManifestWritten and WithTemplatesFrom decode (the judge in mesh-delivery judges what they
answer); Manifest.Predefined, SetPredefined and FormsWritten expose what the moved judge reads; buscompose names its
removals without the catalogue's allow-list; tests outside the catalogue decode, two tree-judging tests moved.

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

go/cmd/mesh-compose/main_test.go

@@ -123,7 +123,7 @@ func TestTheCommandAnswersWhatTheLinkedCompositionAnswers(t *testing.T) {
 		in.Catalogue = map[string]catalogue.Manifest{}
 		for name, m := range r.Cases[0].Manifests {
 			// A request without a list of predefined keys reads a fallback as the indexer does (Request.Predefined).
-			parsed, err := catalogue.ParseManifestForInputs(m.Raw)
+			parsed, err := catalogue.Decode(m.Raw)
 			got := v.Cases[0].Manifests[name]
 			if (err == nil) != got.Accepted || (err != nil && err.Error() != got.Refused) {
 				t.Errorf("%s: the manifest of %s: linked %v, command %+v", depth, name, err, got)