Allow creating fields and components inline from dialogs

- Component dialog: 'New...' button next to field selector creates a
  new field definition and immediately adds it to the component form
- Inventory dialog: same pattern for component selector

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/app.mjs

@@ -1157,6 +1157,23 @@ function open_component_dialog(comp = null) {
 	};
 	add_field_sel.addEventListener('change', add_field_sel._change_handler);
 
+	const new_field_btn = qs(dlg, '#c-new-field');
+	new_field_btn.onclick = () => {
+		const known_ids = new Set(all_fields.map(f => f.id));
+		open_field_dialog(null);
+		document.getElementById('dialog-field').addEventListener('close', () => {
+			const new_field = all_fields.find(f => !known_ids.has(f.id));
+			rebuild_add_select();
+			if (new_field) {
+				active_fields.set(new_field.id, '');
+				rebuild_field_rows();
+				rebuild_add_select();
+				const inputs = field_rows_el.querySelectorAll(`[data-field_id="${new_field.id}"]`);
+				if (inputs.length) inputs[inputs.length - 1].focus();
+			}
+		}, { once: true });
+	};
+
 	component_dialog_callback = async () => {
 		const name = name_input.value.trim();
 		if (!name) return;