fix: restore sidebar header and balance footer sizing

Checks/app-startup.swift

@@ -70,6 +70,30 @@ private enum WindowLayoutCheck {
         sawIntermediateFrame = false
     }
 
+    static func sidebarHeaderIsVisible(in window: NSWindow) -> Bool {
+        guard let content = window.contentView else { return false }
+        let header = NSRect(x: content.bounds.maxX - 84,
+                            y: content.isFlipped ? content.bounds.minY : content.bounds.maxY - 32,
+                            width: 84, height: 32)
+        guard let bitmap = content.bitmapImageRepForCachingDisplay(in: header) else { return false }
+        content.cacheDisplay(in: header, to: bitmap)
+        let scale = CGFloat(bitmap.pixelsWide) / header.width
+        // Each control must paint a visible glyph, not merely exist in the view tree.
+        return (0..<3).allSatisfy { index in
+            var visiblePixels = 0
+            for x in Int(CGFloat(index * 28) * scale)..<Int(CGFloat(index * 28 + 24) * scale) {
+                for y in 0..<bitmap.pixelsHigh {
+                    if let color = bitmap.colorAt(x: x, y: y)?.usingColorSpace(.deviceRGB),
+                       color.alphaComponent > 0.5,
+                       min(color.redComponent, color.greenComponent, color.blueComponent) > 0.5 {
+                        visiblePixels += 1
+                    }
+                }
+            }
+            return visiblePixels >= 8
+        }
+    }
+
     static func advance() {
         let model = PlayerModel.shared
         guard ContinuousClock.now < deadline else { finish("Window layout did not settle at step \(step)"); return }
@@ -95,6 +119,9 @@ private enum WindowLayoutCheck {
         if windowIdentity == nil { windowIdentity = ObjectIdentifier(window) }
         guard ObjectIdentifier(window) == windowIdentity else { finish("Transition replaced the playback window"); return }
         window.layoutIfNeeded()
+        if model.showsQueue && !model.isCompact && !sidebarHeaderIsVisible(in: window) {
+            finish("Sidebar pin, Cast or settings glyph is not visible at step \(step)"); return
+        }
         switch step % 8 {
         case 0, 4:
             if step > 0 {