Fix Steam game mode: clear LD_LIBRARY_PATH, deploy native basic_games, add env var detection

Steam game mode injects its scout/soldier runtime into LD_LIBRARY_PATH,
which breaks Python extension modules and Qt internals that resolve
dependencies via LD_LIBRARY_PATH rather than RPATH. This caused all
Python-based basic_games plugins (Witcher 3, Oblivion Remastered, BG3,
etc.) to fail to load when launched through Steam.

Changes:
- Launcher script: set LD_LIBRARY_PATH to only bundled lib/ dir instead
  of leaving Steam's runtime in the path
- AppRun: same fix — replace rather than append to LD_LIBRARY_PATH
- Deploy libbasic_games_native.so in tarball (was built but never copied)
  so basic_games entries work without Python dependency
- Add STEAM_COMPAT_CLIENT_INSTALL_PATH env var check to Python
  steam_utils.py (mirrors C++ fix from e41a79a) for game mode detection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

3 files changed, 13 insertions, 1 deletions

diff --git a/libs/basic_games/games/game_arkhamcity.py b/libs/basic_games/games/game_arkhamcity.py
index 0b8269f..adcf6d4 100644
--- a/libs/basic_games/games/game_arkhamcity.py
+++ b/libs/basic_games/games/game_arkhamcity.py
@@ -53,7 +53,7 @@ class ArkhamCityGame(BasicGame):
 
     # This will only detect saves from the earliest-created Steam profile on the user's PC.
     def savesDirectory(self) -> QDir:
-        docSaves = QDir(self.documentsDirectory().cleanPath("../../SaveData"))
+        docSaves = QDir(self.documentsDirectory().absoluteFilePath("../../SaveData"))
         if self.is_steam():
             if (steamDir := find_steam_path()) is None:
                 return docSaves
diff --git a/libs/basic_games/games/game_vampirebloodlines.py b/libs/basic_games/games/game_vampirebloodlines.py
index a63b308..41d63cc 100644
--- a/libs/basic_games/games/game_vampirebloodlines.py
+++ b/libs/basic_games/games/game_vampirebloodlines.py
@@ -83,6 +83,7 @@ class VampireTheMasqueradeBloodlinesGame(BasicGame):
         for iniFile in self.iniFiles():
             iniPath = Path(self.documentsDirectory().absoluteFilePath(iniFile))
             if not iniPath.exists():
+                iniPath.parent.mkdir(parents=True, exist_ok=True)
                 with open(iniPath, "w") as _:
                     pass
 
diff --git a/libs/basic_games/steam_utils.py b/libs/basic_games/steam_utils.py
index a3daeaf..f61f392 100644
--- a/libs/basic_games/steam_utils.py
+++ b/libs/basic_games/steam_utils.py
@@ -1,5 +1,6 @@
 # Code greatly inspired by https://github.com/LostDragonist/steam-library-setup-tool
 
+import os
 import sys
 import winreg
 from pathlib import Path
@@ -150,6 +151,16 @@ def find_steam_path() -> Path | None:
     except FileNotFoundError:
         pass
 
+    # When Steam launches an app (e.g. in game mode), it sets
+    # STEAM_COMPAT_CLIENT_INSTALL_PATH to its own root.  Check it first so we
+    # find the right installation even if $HOME resolves differently inside
+    # the gamescope session (e.g. /var/home vs /home on Bazzite).
+    steam_env = os.environ.get("STEAM_COMPAT_CLIENT_INSTALL_PATH", "")
+    if steam_env:
+        p = Path(steam_env)
+        if p.is_dir() and p.joinpath("steamapps", "libraryfolders.vdf").exists():
+            return p
+
     # Linux: check common Steam install locations.
     for candidate in (
         Path.home() / ".local" / "share" / "Steam",