Detect native-Linux Stardew Valley, default executables to no-Proton

Add IPluginGame::isNativeLinux() (virtual, default false) so a plugin
can advertise that the discovered installation is a native Linux build.
Bound through the Python plugin trampoline so basic_games subclasses can
override it.

Stardew Valley plugin: when the install dir contains the StardewValley
launcher script and no Stardew Valley.exe, report isNativeLinux=true and
return Linux-side binary names (StardewValley, StardewModdingAPI). Also
fix GameDataPath to "Mods" — Linux ships the SMAPI mods dir with a
capital M.

ExecutablesList::getPluginExecutables: skip the UseProton flag when the
plugin reports native Linux, so the spawn path falls into launchDirect()
and the game runs without a Wine prefix.

1 files changed, 9 insertions, 0 deletions

diff --git a/libs/uibase/include/uibase/iplugingame.h b/libs/uibase/include/uibase/iplugingame.h
index 0fa2508..93ee09f 100644
--- a/libs/uibase/include/uibase/iplugingame.h
+++ b/libs/uibase/include/uibase/iplugingame.h
@@ -145,6 +145,15 @@ public:
   /**
    * this function may be called before init()
    *
+   * @return true if the discovered installation is a native Linux build that
+   *         should be launched directly without Proton/Wine.  Default false:
+   *         Linux ports of MO2 historically run every game under Proton.
+   */
+  virtual bool isNativeLinux() const { return false; }
+
+  /**
+   * this function may be called before init()
+   *
    * @return an icon for this game
    */
   virtual QIcon gameIcon() const = 0;