fix(ui5-user-menu-item): scope uncheck prevention to showSelection only

Single-select unchecking is now only blocked when the parent item
has showSelection set, so regular single-select groups remain
uncheckable as expected.

Author: SvilenDarvenyashki

packages/fiori/cypress/specs/UserMenu.cy.tsx

@@ -1126,6 +1126,30 @@ describe("UserMenuItem", () => {
 			cy.get("[ui5-user-menu-item][text='Light']")
 				.should("have.attr", "checked");
 		});
+
+		it("allows unchecking in single-select mode when showSelection is false", () => {
+			cy.mount(
+				<>
+					<Button id="openUserMenuBtn">Open User Menu</Button>
+					<UserMenu open={true} opener="openUserMenuBtn">
+						<UserMenuItem text="Options">
+							<UserMenuItemGroup checkMode="Single">
+								<UserMenuItem text="Opt A" checked={true}></UserMenuItem>
+								<UserMenuItem text="Opt B"></UserMenuItem>
+							</UserMenuItemGroup>
+						</UserMenuItem>
+					</UserMenu>
+				</>
+			);
+
+			cy.get("[ui5-user-menu]").find("[ui5-user-menu-item][text='Options']").as("parentItem");
+			cy.get("@parentItem").click();
+
+			cy.get("[ui5-user-menu-item][text='Opt A']").click();
+
+			cy.get("[ui5-user-menu-item][text='Opt A']")
+				.should("not.have.attr", "checked");
+		});
 	});
 
 	describe("UserMenuItemGroup", () => {

packages/fiori/src/UserMenuItem.ts

@@ -61,11 +61,15 @@ class UserMenuItem extends MenuItem {
 
 	/**
 	 * Overrides the base MenuItem behavior to prevent unchecking
-	 * the currently checked item in single-select mode,
-	 * ensuring there is always a selection.
+	 * the currently checked item in single-select mode when
+	 * the parent item uses showSelection, ensuring there is always
+	 * a visible selection.
 	 */
 	_updateCheckedState() {
-		if (this._checkMode === MenuItemGroupCheckMode.Single && this.checked) {
+		const parentItem = this.parentElement?.parentElement;
+		const hasShowSelection = parentItem instanceof UserMenuItem && parentItem.showSelection;
+
+		if (hasShowSelection && this._checkMode === MenuItemGroupCheckMode.Single && this.checked) {
 			return;
 		}
 		super._updateCheckedState();