fix(refresh): mark items so DupeFixer can catch them

[Gqtien]

Menu#openMenu stamps every ItemStack with MenuItemMarker#mark before placing it in the inventory, so DupeFixer.onPickup / onDrop and Menu#cleanInventory can recognize and remove a DeluxeMenus item that ever escapes the menu. MenuHolder#refreshMenu rebuilds the same stacks but skips that call. Any item served after a refresh ([refresh] action, refresh_interval, periodic update task) slips past the dupe fixer.

Fix

Mirror the null-check + mark pattern already used in Menu#openMenu:

                 for (MenuItem item : active) {

                     ItemStack iStack = item.getItemStack(this);

+                    if (iStack == null) {
+                        continue;
+                    }
+
+                    iStack = plugin.getMenuItemMarker().mark(iStack);

                     int slot = item.options().slot();

Demonstration

dm.mp4

A companion plugin rewrites each menu item's lore every tick with its live PDC keys, so the marker state is observable in-game without dumping NBT.

Menu config:

menu_title: '&8Refresh sanitizes PDC'
open_command: demo
size: 27

items:
  diamond:
    material: DIAMOND
    slot: 13
    left_click_commands:
    - '[refresh]'
    right_click_commands:
    - '[openmenu] demo'

On /demo, the diamond's lore reads deluxemenus:dm.

• Without this patch: left-click flips the lore to (no PDC keys). Right-click ([openmenu]) restores it, since Menu#openMenu already marks correctly.
• With this patch: the lore stays on deluxemenus:dm across any number of refreshes.