fix(desktop): align Windows window borders

apps/desktop/src/composables/__tests__/useWindowControls.spec.ts

@@ -14,10 +14,11 @@ describe("window controls", () => {
     expect(shouldShowWindowControls(false, false)).toBe(false);
   });
 
-  it("draws an app frame only for self-decorated desktop windows", () => {
-    expect(shouldDrawDesktopWindowFrame(false, true)).toBe(true);
-    expect(shouldDrawDesktopWindowFrame(true, true)).toBe(false);
-    expect(shouldDrawDesktopWindowFrame(false, false)).toBe(false);
+  it("draws an app frame only for self-decorated non-Windows desktop windows", () => {
+    expect(shouldDrawDesktopWindowFrame(false, true, false)).toBe(true);
+    expect(shouldDrawDesktopWindowFrame(false, true, true)).toBe(false);
+    expect(shouldDrawDesktopWindowFrame(true, true, false)).toBe(false);
+    expect(shouldDrawDesktopWindowFrame(false, false, false)).toBe(false);
   });
 
   it("reserves traffic light inset only for non-fullscreen macOS desktop windows", () => {

apps/desktop/src/composables/useWindowControls.ts

@@ -35,8 +35,10 @@ export function shouldShowWindowControls(isMac: boolean, isDesktop = true): bool
   return isDesktop && !isMac;
 }
 
-export function shouldDrawDesktopWindowFrame(isMac: boolean, isDesktop = true): boolean {
-  return isDesktop && !isMac;
+export function shouldDrawDesktopWindowFrame(isMac: boolean, isDesktop = true, isWindows = false): boolean {
+  // Windows frameless+shadow windows already get a DWM 1px border on all sides.
+  // An extra CSS top hairline stacks on that edge and no longer matches left/right/bottom.
+  return isDesktop && !isMac && !isWindows;
 }
 
 export function useWindowControls() {