fix(launcher): continuous vsync-paced present for stable VRR

The 60fps cap still left 16ms gaps with no present; on windowed G-Sync/FreeSync
DWM keeps moving the window in and out of the VRR path across those gaps and the
refresh rate swings, which the panel shows as flicker. Render continuously
(request_repaint every frame) with vsync on so the window stays continuously in
VRR at the display's own variable refresh.

src/main.rs

@@ -22,6 +22,9 @@ fn main() -> eframe::Result<()> {
             .with_icon(app_icon())
             .with_inner_size([1040.0, 720.0])
             .with_min_inner_size([880.0, 600.0]),
+        // Pair vsync with the display's VRR (G-Sync + Vsync is the recommended
+        // combination): frames present on the monitor's own variable refresh.
+        vsync: true,
         ..Default::default()
     };