Judge the catalogue's manifests against the predefined list, and put merge-check.sh back as main has it (issue 914)

The seats test I moved to internal/ownmanifest parsed each catalogue manifest alone, so claude-code's managed_settings and dunst's font-size, which fall back to a predefined key, were refused where the check clones the catalogue beside (ADR 0348 section 7). It reads them with ReadTreeManifest from the catalogue's root, as the tests that issue 914 fixed do. merge-check.sh differed from main in a comment only; it is main's again.

internal/ownmanifest/seats_test.go

@@ -19,16 +19,25 @@ func TestEveryManifestInUseClaimsASeatTheMeshDefines(t *testing.T) {
 	if len(paths) == 0 {
 		t.Fatal("no manifests in the catalogue, so this proved nothing")
 	}
+	root := beside.Dir(t, "mesh-catalog")
 	paths = append(paths, "../../module.json")
 	var checked int
 	for _, path := range paths {
-		raw, err := os.ReadFile(path)
-		if err != nil {
-			t.Fatal(err)
-		}
 		// The SDK's claimProblems is unexported; the parser runs it on every manifest whose claims are well formed
-		// (go/catalogue manifest.go), so a manifest that parses claims only seats the mesh defines or declares.
-		m, err := catalogue.ParseManifest(raw)
+		// (go/catalogue manifest.go), so a manifest that parses claims only seats the mesh defines or declares. A
+		// catalogue manifest is judged as the merge check judges it, against the predefined list at the root of the tree it
+		// is read in (ADR 0348 §7, issue 914); this repository's own is judged alone.
+		var m catalogue.Manifest
+		var err error
+		if path == "../../module.json" {
+			var raw []byte
+			if raw, err = os.ReadFile(path); err != nil {
+				t.Fatal(err)
+			}
+			m, err = catalogue.ParseManifest(raw)
+		} else {
+			m, err = catalogue.ReadTreeManifest(root, filepath.Dir(path))
+		}
 		if err != nil {
 			t.Errorf("%s: %v", path, err)
 			continue