Publish the real window-fit grid to the TUI before the first frame

src/renderer.rs

@@ -94,6 +94,9 @@ pub fn start(
         (w, r)
     };
 
+    cols_atomic.store((fb_w / cell_w).max(1), Ordering::Release);
+    rows_atomic.store((fb_h / cell_h).max(1), Ordering::Release);
+
     // ----- wgpu -----
     let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
         backends: {