fix(quickshell): start launched apps in their own systemd scopes

app.execute() spawns the app as a child of quickshell, and a child
inherits its parent's cgroup, so everything started from the launcher
ended up inside quickshell.service. systemd kills a unit's whole cgroup
on stop, so a crash or restart of the bar took the open apps with it —
Librewolf counted each one as a crash and eventually stopped restoring
the session at all.

app2unit wraps systemd-run and gives each app its own transient
app-*.scope, the same shape niri gives the windows it spawns itself.
Quickshell 0.3.0 exports no desktop-entry id, only the command, so the
prefix takes that; Terminal=true entries need the -term variant, and a
Path= from the entry travels as a unit property because app2unit
otherwise starts the app in the bar's directory.

defaults/xdg/quickshell/moonarch/LauncherPopout.qml

@@ -37,7 +37,15 @@ Item {
     function launch(app) {
         if (!app)
             return;
-        app.execute();
+        // Started through app2unit, not app.execute(): execute() spawns the app as a child of quickshell,
+        // and a child inherits its parent's cgroup, so the app lands inside quickshell.service and
+        // systemd kills it along with the unit on every restart of the bar. app2unit wraps systemd-run
+        // and hands each app its own transient app-*.scope — the same shape niri gives the windows it
+        // spawns itself. Terminal entries need the -term variant, and a Path= from the entry has to
+        // travel as a unit property because app2unit otherwise starts the app in the bar's directory.
+        const unit = app.runInTerminal ? "app2unit-term" : "app2unit";
+        const props = app.workingDirectory ? ["-p", "WorkingDirectory=" + app.workingDirectory] : [];
+        Quickshell.execDetached([unit].concat(props, ["--"], app.command));
         if (root.popouts)
             root.popouts.close();
     }

defaults/xdg/quickshell/moonarch/NetworkPopout.qml

@@ -408,7 +408,9 @@ PopoutPanel {
         id: managerRow
         width: root.contentWidth
         onClicked: {
-            Quickshell.execDetached(["nm-connection-editor"]);
+            // Through app2unit for the same reason as the launcher: a child of quickshell shares its
+            // cgroup, so a restart of the bar would close the editor mid-edit. See LauncherPopout.
+            Quickshell.execDetached(["app2unit", "--", "nm-connection-editor"]);
             if (root.popouts)
                 root.popouts.close();
         }