i3: other modules' lines are contributions to node-display-session (hq ADR 0212)

rofi, clipmenu, feh, i3status-rust and the laptop's model module wrote files into i3's config.d,
naming no dependency on the window manager. They now contribute their lines; i3 places them under a
line naming each module, and config.d is the operator's alone. The catalogue-wide test composes the
contributions as the controller does and checks the whole with i3 -C.

modules/feh/cmd/feh-tools/manifest_test.go

@@ -63,11 +63,11 @@ func TestFehbgIsOwnedAndTheSessionStartRunsItOnce(t *testing.T) {
 
 func TestTheKeyThatRestoresTheWallpaperIsAnI3DropIn(t *testing.T) {
 	m := readManifest(t)
-	m.sameAsSource(t, "i3-bindings", "files/i3/50-feh.conf")
-	if p := m.resource(t, "i3-bindings")["path"]; p != "${machine:account-home}/.config/i3/config.d/50-feh.conf" {
+	m.i3LinesAreSource(t, "files/i3/50-feh.conf")
+	if p := m.i3Lines(); p == "" {
 		t.Fatalf("path: %v", p)
 	}
-	if c := m.resource(t, "i3-bindings")["content"].(string); !strings.Contains(c, "bindsym $mod+Shift+b exec --no-startup-id ~/.fehbg\n") {
+	if c := m.i3Lines(); !strings.Contains(c, "bindsym $mod+Shift+b exec --no-startup-id ~/.fehbg\n") {
 		t.Fatalf("%s", c)
 	}
 }