itemsRegistry is a Java Object. getItems returns a Java java.util.List Object, not a JavaScript list. So the JavaScript stuff won’t work. You’ll either need to convert it to a JavaScript list so you can filter it in the usual JavaScript ways, or filter it using Java’s stream API.
Convert to a JavaScript List and filter:
var items = Java.from(itemRegistry.getItems('Kitchen_.*')).filter(item => item.hasTag("Light"));
Note that items will be a JavaScript Array
To use Java’s stream API:
var items = itemRegistry.getItems('Kitchen_.*').stream().filter(function(item) { return item.hasTag("Light"); });
items will be a java.util.List and not a JavaScript Array.
Note I just typed these two examples in. There may be a typo.