fix(email): Remove false "free shipping" promise from mentor gift card email

src/email/templates/giftCard.md

@@ -7,7 +7,7 @@ In recognition, we'd like to send you [{{ featuredProduct }}]({{link}}). (Or you
 In recognition, we're sending you a ${{ amount }} giftcard for [the CodeDay Store]({{link}}).
 {{/if}}
 
-Use this code at checkout to receive the ${{amount}} credit with free shipping: <strong>{{code}}</strong>
+Use this code at checkout to receive the ${{amount}} credit: <strong>{{code}}</strong>
 
 This code expires in a month, so [click here to use it now.]({{ link }})
 

tests/testGiftCardTemplate.ts

@@ -0,0 +1,18 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { readFile } from 'fs/promises';
+import path from 'path';
+
+// The mentor-giftcard Shopify discount is a `discountCodeBasicCreate` amount-off
+// discount, which only reduces the eligible item subtotal and CANNOT waive the
+// shipping line. The gift email must therefore never promise "free shipping",
+// or mentors will be asked to pay an unexpected shipping charge at checkout for
+// a "free" gift. This guard fails if that false promise is re-introduced.
+test('giftCard.md does not promise free shipping (Shopify discountAmount cannot waive shipping)', async () => {
+  const src = (await readFile(path.join(__dirname, '..', 'src', 'email', 'templates', 'giftCard.md'))).toString();
+  assert.equal(
+    /free\s+shipping/i.test(src),
+    false,
+    'giftCard.md must not promise "free shipping": the issued discountCodeBasicCreate discountAmount only applies to the item subtotal, not the shipping line',
+  );
+});