Add auto-close on selection for item picker modal in single-selection mode

When selectionMode is 'single', clicking an item now immediately submits and closes
the modal, providing a streamlined UX. Multiple selection mode continues to require
explicit confirmation via the confirm button.

This improves the user experience for profile-picker and context-picker components
when used in single-item mode, as users no longer need to click an additional
"Close" button after selecting an item.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: mattbrailsford

Umbraco.Ai/src/Umbraco.Ai.Web.StaticAssets/Client/src/core/modals/item-picker/item-picker-modal.element.ts

@@ -68,6 +68,7 @@ export class UaiItemPickerModalElement extends UmbModalBaseElement<
             // Single selection - submit immediately
             this.updateValue({ selection: [item] });
             this.modalContext?.dispatchEvent(new UaiSelectedEvent(item.value, item));
+            this._submitModal();
         }
 	}