fix: Menu triggers no longer take focus when they are mounted (#25016)

This is likely a regression from #24738. Specifically, the removal of `shouldHandleKeyboardRef` from useMenu.tsx is causing it to always call `state.triggerRef.current?.focus()` when mounted.

change/@fluentui-react-menu-be54a5cf-5794-430d-a10e-a84b223e4eef.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: Menu triggers no longer take focus when they are mounted",
+  "packageName": "@fluentui/react-menu",
+  "email": "behowell@microsoft.com",
+  "dependentChangeType": "patch"
+}

packages/react-components/react-menu/e2e/Menu.e2e.tsx

@@ -115,6 +115,22 @@ describe('MenuTrigger', () => {
       cy.get(menuSelector).should('be.visible').get(menuItemSelector).first().should('be.focused');
     });
   });
+
+  it('should not automatically focus itself when mounted', () => {
+    mount(
+      <Menu>
+        <MenuTrigger>
+          <button>Menu</button>
+        </MenuTrigger>
+        <MenuPopover>
+          <MenuList>
+            <MenuItem>Item</MenuItem>
+          </MenuList>
+        </MenuPopover>
+      </Menu>,
+    );
+    cy.get(menuTriggerSelector).should('not.be.focused');
+  });
 });
 
 describe('Custom Trigger', () => {

packages/react-components/react-menu/src/components/Menu/useMenu.tsx

@@ -162,6 +162,7 @@ const useMenuOpenState = (
   const parentSetOpen = useMenuContext_unstable(context => context.setOpen);
   const onOpenChange: MenuState['onOpenChange'] = useEventCallback((e, data) => state.onOpenChange?.(e, data));
 
+  const shouldHandleKeyboardRef = React.useRef(false);
   const shouldHandleTabRef = React.useRef(false);
   const pressedShiftRef = React.useRef(false);
   const setOpenTimeout = React.useRef(0);
@@ -185,6 +186,7 @@ const useMenuOpenState = (
     }
 
     if (e.type === 'keydown' && (e as React.KeyboardEvent<HTMLElement>).key === Tab) {
+      shouldHandleKeyboardRef.current = true;
       shouldHandleTabRef.current = true;
       pressedShiftRef.current = (e as React.KeyboardEvent<HTMLElement>).shiftKey;
     }
@@ -288,14 +290,15 @@ const useMenuOpenState = (
       focusFirst();
     }
 
-    if (!open) {
+    if (shouldHandleKeyboardRef.current && !open) {
       if (shouldHandleTabRef.current && !state.isSubmenu) {
         pressedShiftRef.current ? focusBeforeMenuTrigger() : focusAfterMenuTrigger();
       } else {
         state.triggerRef.current?.focus();
       }
     }
 
+    shouldHandleKeyboardRef.current = false;
     shouldHandleTabRef.current = false;
     pressedShiftRef.current = false;
   }, [state.triggerRef, state.isSubmenu, open, focusFirst, focusAfterMenuTrigger, focusBeforeMenuTrigger]);