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/app.rs

@@ -1804,15 +1804,15 @@ impl LauncherApp {
 
 impl eframe::App for LauncherApp {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
-        // Present at a steady ~60 FPS while the window is open. egui is normally
-        // reactive and would idle at ~2 FPS (a 500 ms repaint), but on a G-Sync /
-        // FreeSync (VRR) display that sits below the VRR floor: the panel engages
-        // low-framerate compensation, and every hover/animation briefly spikes the
-        // rate and drops back, so the refresh rate keeps swinging and the panel
-        // visibly flickers. A constant, in-range cadence gives VRR a single rate to
-        // lock onto and removes the flicker. 16 ms is monitor-independent and cheap
-        // for a UI this small; vsync (on by default) keeps present times regular.
-        ctx.request_repaint_after(std::time::Duration::from_millis(16));
+        // Render continuously (present every vsync) instead of reactively. egui
+        // normally idles at a low, bursty repaint rate; on a G-Sync / FreeSync
+        // (VRR) display a windowed app that presents in bursts with idle gaps
+        // makes DWM keep moving the window in and out of the VRR path and the
+        // refresh rate swing — which the panel shows as flicker. Presenting on
+        // every frame keeps the window continuously in VRR at the display's own
+        // (variable) refresh, which is stable. vsync (on by default) paces this to
+        // the monitor rather than spinning uncapped.
+        ctx.request_repaint();
         self.drive_restart_queue();
 
         egui::TopBottomPanel::top("header")

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()
     };