fix(linux): remove unnecessary desktopCapturer call from display media handler

The setDisplayMediaRequestHandler was calling desktopCapturer.getSources()
to provide a video source that the renderer never uses (it requests
video: false and only consumes audio tracks). On Wayland, this created a
new xdg-desktop-portal ScreenCast session on every launch, showing an
unavoidable screen share dialog because Electron does not persist
PipeWire restore tokens across desktopCapturer sessions.

Simplified the handler to return only { audio: 'loopback' }, which
captures system audio via PipeWire/PulseAudio monitor source without
any portal interaction.

src/main/index.ts

@@ -5,7 +5,6 @@ import {
     app,
     BrowserWindow,
     BrowserWindowConstructorOptions,
-    desktopCapturer,
     globalShortcut,
     ipcMain,
     Menu,
@@ -734,19 +733,7 @@ async function createWindow(first = true): Promise<void> {
     });
 
     mainWindow.webContents.session.setDisplayMediaRequestHandler((_request, callback) => {
-        desktopCapturer
-            .getSources({ types: ['screen'] })
-            .then((sources) => {
-                if (sources.length > 0) {
-                    callback({ audio: 'loopback', video: sources[0] });
-                } else {
-                    callback({});
-                }
-            })
-            .catch((err) => {
-                log.warn('desktopCapturer.getSources failed', err);
-                callback({});
-            });
+        callback({ audio: 'loopback' });
     });
 
     if (!disableAutoUpdates() && store.get('disable_auto_updates') !== true) {