fix(screen-share): preset dims no longer crop non-16:9 monitors

Pass width/height as { ideal: N } constraints (not exact values) so
Chromium preserves the source's aspect ratio instead of cropping
non-matching monitors. Previously a 1920x1200 monitor under a 1080p
preset lost the bottom 120px including the Windows taskbar.

The auto-preset fallback now omits width/height entirely (both set to
undefined) so getDisplayMedia uses the screen's native resolution.
Cast through `unknown` to satisfy LiveKit's VideoResolution type, which
declares width/height as plain number but Chromium accepts the full
MediaTrackConstraints shape at runtime.

apps/desktop/src/context/CallContext.tsx

@@ -1442,20 +1442,29 @@ export function CallProvider({ children }: { children: ReactNode }) {
           // the same system audio twice and Chromium's version would
           // include our own renderer playback.
           audio: preferNativeLoopback ? false : wantAudio,
+          // Preset dims are passed as `ideal` constraints (not fixed width/height)
+          // so Chromium picks the closest match preserving the source's aspect
+          // ratio instead of CROPPING non-matching monitors. Without this, a 16:10
+          // monitor (1920×1200, 2560×1600) streamed under a 16:9 preset loses its
+          // bottom strip — including the Windows taskbar.
+          //
+          // LiveKit's VideoResolution types declare width/height as `number`, but
+          // Chromium's getDisplayMedia accepts the full MediaTrackConstraints shape
+          // including { ideal: N } objects — we cast through `unknown` to satisfy tsc.
           ...(ssParams.dims
             ? {
                 resolution: {
-                  width: ssParams.dims.width,
+                  width: { ideal: ssParams.dims.width },
-                  height: ssParams.dims.height,
+                  height: { ideal: ssParams.dims.height },
                   frameRate: fps,
-                },
+                } as unknown as { width: number; height: number; frameRate: number },
               }
             : {
                 resolution: {
-                  width: 3840,
-                  height: 2160,
                   frameRate: fps,
-                },
+                  width: undefined,
+                  height: undefined,
+                } as unknown as { width: number; height: number; frameRate: number },
               }),
           ...(displaySurface
             ? ({ displaySurface } as { displaySurface: DisplaySurfaceHint })