Deduplicate games found from multiple sources

When a game appears as both a Steam manifest and an XDG
desktop entry, drop the desktop duplicate. Steam entries are
preferred because they carry cover artwork and route through
the Steam launcher for Proton compatibility.

components/gamingshellplugin/gamelauncherprovider.cpp

@@ -92,6 +92,10 @@ void GameLauncherProvider::refresh()
     loadFlatpakGames();
     loadRecentTimestamps();
 
+    // Deduplicate: when the same game appears from multiple sources,
+    // prefer Steam (has artwork + Proton handling) over desktop.
+    deduplicateGames();
+
     // Sort alphabetically, case-insensitive
     std::sort(m_allGames.begin(), m_allGames.end(), [](const GameEntry &a, const GameEntry &b) {
         return a.name.compare(b.name, Qt::CaseInsensitive) < 0;
@@ -182,6 +186,25 @@ void GameLauncherProvider::launchByStorageId(const QString &storageId)
     }
 }
 
+void GameLauncherProvider::deduplicateGames()
+{
+    // Build a set of names from Steam entries (case-insensitive).
+    QSet<QString> steamNames;
+    for (const auto &g : std::as_const(m_allGames)) {
+        if (g.source == QLatin1String("steam")) {
+            steamNames.insert(g.name.toLower());
+        }
+    }
+
+    // Remove desktop entries whose name matches a Steam entry.
+    m_allGames.erase(std::remove_if(m_allGames.begin(),
+                                    m_allGames.end(),
+                                    [&steamNames](const GameEntry &g) {
+                                        return g.source == QLatin1String("desktop") && steamNames.contains(g.name.toLower());
+                                    }),
+                     m_allGames.end());
+}
+
 // --- XDG .desktop games ---
 
 void GameLauncherProvider::loadDesktopGames()

components/gamingshellplugin/gamelauncherprovider.h

@@ -74,6 +74,7 @@ private:
     void loadDesktopGames();
     void loadSteamGames();
     void loadFlatpakGames();
+    void deduplicateGames();
     void loadRecentTimestamps();
     void saveRecentTimestamp(const QString &storageId, const QDateTime &when);
     void applyFilter();