SilentSDDM install: quiet like everything else

The theme's own install.sh runs dnf for its dependencies and its
output flooded the screen raw (laptop-proven: the last wall of text
left in the run). Now wrapped in ui_quiet_run: live block line with
the current dependency, summary count after, full output in the
setup log, red + tail on failure. Unattended/piped runs keep plain
output. pipefail still suspended around the yes| pipe (inherited at
subshell fork).

setup.sh

@@ -762,9 +762,13 @@ if pkg_installed sddm; then
 
     if [[ -f "$REPO_DIR/install.sh" ]]; then
         # yes | install.sh: the installer prompts; SIGPIPE from 'yes' would
-        # read as a crash under pipefail, so suspend it for this one command
+        # read as a crash under pipefail, so suspend it for this one command.
+        # pipefail state is inherited by the ui_quiet_run subshell at fork.
+        # The theme's own dnf dependency flood goes to the log like every
+        # other transaction (laptop-proven it was the last raw wall left).
         set +o pipefail
-        if ( cd "$REPO_DIR" && yes | ./install.sh ); then
+        if ui_quiet_run "Installing SilentSDDM theme" \
+            bash -c 'cd "$1" && yes | ./install.sh' _ "$REPO_DIR"; then
             ok "SilentSDDM theme installed."
         else
             color_red "  Failed: SilentSDDM installer (continuing; SDDM keeps its default theme)"