Switch SteamOS to software rendering for webview stability

Replaces hardware acceleration and ANGLE-based GPU flags with software rendering on SteamOS to address webview rendering issues under Gamescope. Updates both main.js and the start:steamos script in package.json to disable GPU compositing and enforce software rendering.

main.js

@@ -59,19 +59,22 @@ if (process.platform === 'linux') {
   
   if (isSteamOS) {
     console.log(`[GPU] SteamOS/Gamescope DETECTED: ${detectionReason}`);
-    console.log('[GPU] Applying SteamOS-specific GPU flags for webview rendering...');
+    console.log('[GPU] Disabling hardware acceleration - using software rendering...');
     
-    // SteamOS GPU flags - use ANGLE for rendering
+    // On SteamOS, hardware acceleration causes webview rendering issues
+    // Software rendering is more stable under Gamescope
+    app.disableHardwareAcceleration();
+    
+    // Ozone platform
     app.commandLine.appendSwitch('ozone-platform', 'x11');
-    app.commandLine.appendSwitch('use-angle', 'gl');
-    app.commandLine.appendSwitch('angle-platform-type', 'x11');
     
-    // GPU process settings
-    app.commandLine.appendSwitch('in-process-gpu');
-    app.commandLine.appendSwitch('disable-gpu-vsync');
+    // Disable GPU compositing completely - use software
+    app.commandLine.appendSwitch('disable-gpu');
+    app.commandLine.appendSwitch('disable-gpu-compositing');
+    app.commandLine.appendSwitch('disable-software-rasterizer');
     
     // Feature flags
-    app.commandLine.appendSwitch('enable-features', 'VulkanFromANGLE,UseOzonePlatform');
+    app.commandLine.appendSwitch('enable-features', 'UseOzonePlatform');
     app.commandLine.appendSwitch('disable-features', 'VizDisplayCompositor');
   } else {
     console.log('[GPU] Standard Linux environment detected');