fix: remove setDisplayMediaRequestHandler to let restrictOwnAudio work natively

The custom screen share picker intercepted getDisplayMedia() and created
a raw loopback stream, bypassing Chromium's constraint pipeline entirely.
restrictOwnAudio was silently discarded. Removing the handler lets
Chromium 144's native getDisplayMedia run end-to-end with restrictOwnAudio
applied, eliminating the audio feedback loop in the desktop app.

packages/desktop/src/preload.ts

@@ -50,14 +50,6 @@ contextBridge.exposeInMainWorld('backspace', {
     ipcRenderer.on('deep-link', (_event, url) => callback(url));
   },
 
-  // Screen share picker coordination
-  onScreenShareSources: (callback: (sources: unknown[]) => void) => {
-    ipcRenderer.on('screen-share-sources', (_event, sources) => callback(sources));
-  },
-  selectScreenSource: (sourceId: string | null, shareAudio?: boolean) => {
-    ipcRenderer.send('screen-share-selected', sourceId, shareAudio ?? true);
-  },
-
   // Instance URL management
   getInstanceUrl: () => ipcRenderer.invoke('get-instance-url'),
   setInstanceUrl: (url: string) => ipcRenderer.invoke('set-instance-url', url),