Harden transient scope lifecycle

Improve GameCenter daemon handling of systemd transient scopes.

- Watch monitored-launch scopes early and avoid dropping Launching sessions
  when the unit disappears before PIDs are attached.
- Stop leaked scopes on AttachProcessesToUnit failures.
- Make Stop() resilient for recovered sessions by falling back to TERM/KILL
  on scope PIDs when StopUnit fails unexpectedly.
- Only recover scopes that match the expected A-La-Karte description.

src/gamecenter/gamecenterdaemon.cpp

@@ -803,6 +803,18 @@ void GameCenterDaemon::handleSystemdUnitRemoved(const QString &unitName, const Q
         return;
     }
 
+    if (sit.value().scanner) {
+        if (!sit.value().unitPath.path().isEmpty()) {
+            const QString unitPathKey = sit.value().unitPath.path();
+            m_unitPathToSessionId.remove(unitPathKey);
+            if (QObject *watcher = m_unitPathWatchers.take(unitPathKey)) {
+                watcher->deleteLater();
+            }
+        }
+        sit.value().unitPath = {};
+        return;
+    }
+
     unwatchSystemdUnit(sit.value().unitName, sit.value().unitPath);
     removeSessionInternal(sessionId, sit.value().stopping ? QStringLiteral("Stopped") : QStringLiteral("Exited"));
 }
@@ -833,6 +845,25 @@ void GameCenterDaemon::handleSystemdUnitPropertiesChanged(const QDBusObjectPath
     }
     const QString activeState = activeStateV.toString();
 
+    if (sit.value().scanner) {
+        if (activeState == QLatin1String("active") || activeState == QLatin1String("activating") || activeState == QLatin1String("deactivating")) {
+            const QList<uint> pids = m_systemd.scopePids(unitPath);
+            if (!pids.isEmpty()) {
+                sit.value().mainPid = pids.first();
+            }
+        } else {
+            const QString unitPathKey = unitPath.path();
+            m_unitPathToSessionId.remove(unitPathKey);
+            if (QObject *watcher = m_unitPathWatchers.take(unitPathKey)) {
+                watcher->deleteLater();
+            }
+            sit.value().unitPath = {};
+        }
+
+        Q_EMIT SessionChanged(sessionToVariantMap(sit.value(), sessionState(sit.value())));
+        return;
+    }
+
     if (activeState == QLatin1String("active") || activeState == QLatin1String("activating") || activeState == QLatin1String("deactivating")) {
         const QList<uint> pids = m_systemd.scopePids(unitPath);
         if (!pids.isEmpty()) {
@@ -1495,6 +1526,8 @@ QString GameCenterDaemon::launchMonitored(const QVariantMap &launchSpec, const Q
 
     m_sessions[sessionId] = session;
 
+    watchSystemdUnit(sessionId, session.unitName, session.unitPath);
+
     connect(bootstrap, qOverload<int, QProcess::ExitStatus>(&QProcess::finished), this, [this, sessionId](int, QProcess::ExitStatus) {
         const auto it = m_sessions.find(sessionId);
         if (it == m_sessions.end()) {
@@ -1609,6 +1642,11 @@ void GameCenterDaemon::attachPidsToSession(const QString &sessionId, const QList
                 {QStringLiteral("error"), attachReply.error().message()},
             };
 
+            if (!it.value().unitName.isEmpty()) {
+                m_systemd.stopUnit(it.value().unitName);
+                unwatchSystemdUnit(it.value().unitName, it.value().unitPath);
+            }
+
             QVariantMap finalState = sessionToVariantMap(it.value(), QStringLiteral("Failed"));
             if (it.value().process) {
                 it.value().process->deleteLater();
@@ -1780,6 +1818,32 @@ void GameCenterDaemon::Stop(const QString &sessionId)
             return;
         }
 
+        QDBusObjectPath unitPath = it.value().unitPath;
+        if (unitPath.path().isEmpty()) {
+            const QDBusReply<QDBusObjectPath> getUnitReply = m_systemd.getUnit(it.value().unitName);
+            if (getUnitReply.isValid()) {
+                unitPath = getUnitReply.value();
+                it.value().unitPath = unitPath;
+                watchSystemdUnit(sessionId, it.value().unitName, unitPath);
+            }
+        }
+
+        QList<uint> pids;
+        if (!unitPath.path().isEmpty()) {
+            pids = m_systemd.scopePids(unitPath);
+        }
+        if (pids.isEmpty() && it.value().mainPid > 0) {
+            pids = {it.value().mainPid};
+        }
+        if (!pids.isEmpty()) {
+            terminatePids(pids);
+            QTimer::singleShot(5000, this, [pids]() {
+                killPids(pids);
+            });
+            Q_EMIT SessionChanged(sessionToVariantMap(it.value(), QStringLiteral("Stopping")));
+            return;
+        }
+
         if (it.value().process && it.value().process->state() != QProcess::NotRunning) {
             it.value().process->terminate();
             QTimer::singleShot(5000, it.value().process, [process = it.value().process]() {
@@ -1886,7 +1950,8 @@ void GameCenterDaemon::recoverExistingSessions()
 
     static const QString prefix = QStringLiteral("alakarte-game-");
     static const QString suffix = QStringLiteral(".scope");
-    static const QString descPrefix = QStringLiteral("A-La-Karte game ");
+    static const QString descBase = QStringLiteral("A-La-Karte game");
+    static const QString descPrefix = descBase + QLatin1Char(' ');
 
     const SystemdUnitInfoList units = reply.value();
     for (const SystemdUnitInfo &unit : units) {
@@ -1897,6 +1962,10 @@ void GameCenterDaemon::recoverExistingSessions()
             continue;
         }
 
+        if (unit.description != descBase && !unit.description.startsWith(descPrefix)) {
+            continue;
+        }
+
         const QString sessionId = unit.name.mid(prefix.length(), unit.name.length() - prefix.length() - suffix.length());
         if (sessionId.isEmpty() || m_sessions.contains(sessionId)) {
             continue;