WebView2 silently denies getUserMedia() unless a PermissionRequested
handler explicitly allows it. macOS was already covered by Info.plist;
Windows had nothing. Adds a COM event handler via with_webview that
auto-approves mic and camera requests so Element Call voice/video
works in the desktop app.
Also includes previously uncommitted changes:
- tauri.conf.json: add media-src / mediastream: to CSP
- Info.plist: macOS NSMicrophoneUsageDescription / NSCameraUsageDescription
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
