refactor(radio): expose shared country normalization

src/data/radioCountry.test.mjs

@@ -1,6 +1,6 @@
 import assert from 'node:assert/strict';
 import test from 'node:test';
-import { normalizeRadioCountryInput } from './radioCountry.js';
+import { normalizeRadioCountryInput } from '../layers/radio/index.js';
 
 test('Radio country normalization maps ISO codes and bounded common names', () => {
   for (const [input, code] of [

src/layers/radio/index.js

@@ -138,3 +138,5 @@ export {
   radioTunerPointerPosition,
   buildRadioTunerTicks,
 } from '../../ui/radioTunerModel.js';
+
+export { normalizeRadioCountryInput } from '../../data/radioCountry.js';