A setting reaches only what declares it, the mesh places its own files, registration refuses a name

Three of novox/hq's group-4 leftovers, one branch.

Issue 173: a module's settings reached every route it contributed, every database it asked for and
every served fact its consumers read — a mail server's site name arrived at the proxy as a route
fact. A setting now overrides a key a contribution or served fact declares and adds none; a file
still merges any key, and a key nothing takes is named as stray instead of dropped silently.

Issue 174: the mesh's own files for a module — its bus credential, its merged config, its bindings —
were placed by the definition under /var/lib/mesh/<module>, 232 host paths in 50 definitions. A
directory may now say `place: "mesh"` and resolves to <root>/mesh/<module>; a directory beneath a
placed one may state its path as `${dir:<id>}/<rest>` and moves with it. The proof test resolves
both catalogues and compares: 48 definitions, no path moved. The controller's own manifest is
converted here; the catalogue in mesh-catalog.

ADR 0155: the installation check moves to registration. `module add` and a build's result both
refuse a definition that names an installation, in the check's words, with the way out; the build
stays recorded.

internal/catalogue/contributes_test.go

@@ -197,6 +197,27 @@ func TestARouteCanBeSetPerMesh(t *testing.T) {
 	}
 }
 
+func TestASettingReachesAContributionOnlyWhereItDeclaresTheKey(t *testing.T) {
+	// novox/hq 04-ISSUES/173: the mail module's site name, set so its environment file could read
+	// it, arrived in every route it contributed. A setting overrides a key the contribution
+	// declares and adds none — the provider reads the contribution as a contract.
+	got, _ := Resolve(shelf(proxy(), published("board", "board", 8080)), []string{"board"}, workstation(), World{})
+
+	out, err := got.Declaration(Rendering{Settings: SettingsBy{
+		"board": {{From: "the mesh", Values: map[string]any{"host": "dashboard", "sitename": "Board"}}},
+	}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	given := received(t, out)
+	if given[0].Values["host"] != "dashboard" {
+		t.Fatalf("the setting did not override the route's host: %v", given[0].Values)
+	}
+	if _, leaked := given[0].Values["sitename"]; leaked {
+		t.Fatalf("a setting the route never declared reached the proxy: %v", given[0].Values)
+	}
+}
+
 func TestReceivingWhatYouDoNotProvideIsRefused(t *testing.T) {
 	// It would create a file nobody ever writes to, on a machine where nothing asked for it.
 	_, err := ParseManifest([]byte(`{"module":"traefik","version":"1",