Make boot greeter frameless and match Gaming display mode

scripts/greeter-check.py

@@ -21,7 +21,14 @@ s = (
 )
 s = (
     s.rstrip()[:-1]
-    + """    IpcHandler { target: "test"; function submit(password: string): void { auth.submitted(password); } }
+    + """    IpcHandler {
+        target: "test"
+        function submit(password: string): void { auth.submitted(password); }
+        function closeCheck(): bool {
+            root.close();
+            return root.visible && (root.flags & Qt.FramelessWindowHint) !== 0;
+        }
+    }
 }
 """
 )
@@ -62,6 +69,19 @@ try:
         data = json.dumps(value).encode()
         conn.sendall(struct.pack("<I", len(data)) + data)
 
+    for _ in range(30):
+        result = sp.run(
+            [qs, "ipc", "--pid", str(proc.pid), "call", "test", "closeCheck"],
+            env=env, capture_output=True, text=True,
+        )
+        if result.returncode == 0:
+            assert result.stdout.strip() == "true", result.stdout
+            break
+        time.sleep(0.1)
+    else:
+        raise AssertionError(result.stderr)
+    assert proc.poll() is None, "Closing the greeter must not exit it"
+
     def submit():
         for _ in range(30):
             result = sp.run(
@@ -120,7 +140,7 @@ try:
             send({"type": "success"})
             time.sleep(0.3)
     print(
-        "Greeter: failed password does not launch; retry and authenticated launch pass"
+        "Greeter: frameless window rejects close; failed password does not launch; retry and authenticated launch pass"
     )
 finally:
     proc.terminate()