fix: ZDelete! includes zpack.nvim in deletion list

Append zpack.nvim at the end of the delete list so it gets deleted
last, after all other plugins in reverse priority order.

Author: zuqini

lua/zpack/commands.lua

@@ -224,6 +224,7 @@ M.setup = function(prefix)
       for i = #state.registered_plugins, 1, -1 do
         table.insert(names, state.registered_plugins[i].name)
       end
+      table.insert(names, 'zpack.nvim')
 
       util.schedule_notify(("Deleting all %d installed plugin(s)..."):format(#names), vim.log.levels.INFO)
       vim.pack.del(names, { force = true })

tests/zdelete_test.lua

@@ -49,7 +49,8 @@ return function()
       local call = _G.test_state.vim_pack_del_calls[1]
       helpers.assert_not_nil(call.opts, "opts should be passed to vim.pack.del")
       helpers.assert_true(call.opts.force, "force option should be true")
-      helpers.assert_equal(#call.names, 3, "all 3 plugins should be in delete list")
+      helpers.assert_equal(#call.names, 4, "all 4 plugins (3 + zpack.nvim) should be in delete list")
+      helpers.assert_table_contains(call.names, 'zpack.nvim', "zpack.nvim should be in delete list")
 
       helpers.cleanup_test_env()
       helpers.delete_zpack_commands()