feat(plugin): add MangoHud status check and config writing to backend

plugins/decky-vault/main.py

@@ -53,4 +53,67 @@ class Plugin:
         """RPC: Set a single setting and persist. Returns updated settings."""
         self._settings[key] = value
         self._write_settings(self._settings)
-        return self._settings
+        return self._settings
+
+    async def check_mangohud(self) -> dict:
+        """RPC: Check if MangoHud is installed. Returns {installed: bool, path: str, version: str}."""
+        import subprocess
+        try:
+            result = subprocess.run(
+                ["which", "mangohud"],
+                capture_output=True, text=True, timeout=5
+            )
+            if result.returncode == 0:
+                mangohud_path = result.stdout.strip()
+                # Get version
+                version_result = subprocess.run(
+                    ["mangohud", "--version"],
+                    capture_output=True, text=True, timeout=5
+                )
+                version = version_result.stdout.strip() if version_result.returncode == 0 else "unknown"
+                return {"installed": True, "path": mangohud_path, "version": version}
+            else:
+                return {"installed": False, "path": "", "version": ""}
+        except Exception as e:
+            return {"installed": False, "path": "", "version": "", "error": str(e)}
+
+    async def write_mangohud_config(self) -> dict:
+        """RPC: Write the MangoHud logging config to ~/.config/MangoHud/MangoHud.conf.
+        Returns {success: bool, path: str, error: str?}."""
+        try:
+            home = os.path.expanduser("~")
+            config_dir = os.path.join(home, ".config", "MangoHud")
+            config_path = os.path.join(config_dir, "MangoHud.conf")
+            os.makedirs(config_dir, exist_ok=True)
+
+            # MangoHud config that enables logging with the metrics we need.
+            # output_folder is required for logging to work.
+            # We log to /tmp so the plugin can read it after the session.
+            config_content = """\
+# DeckyVault MangoHud logging config
+output_folder=/tmp
+output_file=deckyvault-mangohud.log
+log_duration=0
+fps
+frame_timing
+cpu_power
+gpu_power
+cpu_temp
+gpu_temp
+benchmark_percentiles=97,AVG,1,0.1
+"""
+            with open(config_path, 'w') as f:
+                f.write(config_content)
+
+            return {"success": True, "path": config_path}
+        except Exception as e:
+            return {"success": False, "path": "", "error": str(e)}
+
+    async def get_mangohud_config(self) -> dict:
+        """RPC: Read the current MangoHud config. Returns {exists: bool, content: str, path: str}."""
+        home = os.path.expanduser("~")
+        config_path = os.path.join(home, ".config", "MangoHud", "MangoHud.conf")
+        if os.path.exists(config_path):
+            with open(config_path, 'r') as f:
+                return {"exists": True, "content": f.read(), "path": config_path}
+        return {"exists": False, "content": "", "path": config_path}