fix(shop): render a bag offer's capacity line once, not twice

`resolveTarget` gave a bag target the same string for `description` and
`effectSummary`, and the shop row renders both, so the slice's two flagship
offers showed "Capacity: 5 Raider Trophies" on consecutive lines. Spec §5's
worked example shows it once.

A bag definition carries no flavour text of its own, so the description is now
empty and the row omits the span entirely rather than emitting an empty one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

apps/api/src/shops/shop.service.ts

@@ -307,9 +307,11 @@ export class ShopService {
         definitionId: offer.lootBagDefinition.id,
         key: offer.lootBagDefinition.key,
         name: offer.lootBagDefinition.name,
-        // A bag definition carries no flavour text of its own; the capacity
-        // line is the honest description of what it is.
-        description: describeBagEffect(offer.lootBagDefinition),
+        // A bag definition carries no flavour text of its own. The capacity
+        // line is the whole of what there is to say about it, and it is already
+        // carried by `effectSummary`; repeating it here would render it twice
+        // (slice §5 shows the line once).
+        description: '',
         iconPath: offer.lootBagDefinition.iconPath,
         effectSummary: describeBagEffect(offer.lootBagDefinition),
       };

apps/web/src/app/features/npc/merchant-page.component.html

@@ -234,9 +234,11 @@
               />
               <div class="shop-row__naming">
                 <span class="shop-row__name">{{ offer.itemName }}</span>
-                <span class="shop-row__description">{{
-                  offer.itemDescription
-                }}</span>
+                @if (offer.itemDescription) {
+                  <span class="shop-row__description">{{
+                    offer.itemDescription
+                  }}</span>
+                }
                 @if (offer.effectSummary) {
                   <span class="shop-row__effect" data-effect>{{
                     offer.effectSummary

apps/web/src/app/features/npc/merchant-page.component.spec.ts

@@ -232,6 +232,11 @@ async function renderMerchantWithShop(
   return { fixture, element, store };
 }
 
+/** How many times `needle` shows up in `haystack` -- `toContain` cannot say. */
+function countOccurrences(haystack: string, needle: string): number {
+  return haystack.split(needle).length - 1;
+}
+
 describe('MerchantPageComponent', () => {
   afterEach(() => TestBed.resetTestingModule());
 
@@ -383,13 +388,15 @@ describe('MerchantPageComponent', () => {
 
   it('shows the requirement and the current value on a locked offer', async () => {
     // A visible lock with a number attached is a goal; a hidden offer is not
-    // (slice §5).
+    // (slice §5). Shaped like the real Trophy Pouch offer: a bag definition
+    // carries no flavour text, so the API sends an empty description and the
+    // capacity line arrives once, as the effect.
     const { fixture } = await renderMerchantWithShop({
       offers: [
         {
           itemKey: 'basic-trophy-pouch',
           itemName: 'Basic Trophy Pouch',
-          itemDescription: 'Capacity: 5 Raider Trophies',
+          itemDescription: '',
           iconPath: '/images/items/basic-trophy-pouch.png',
           currencyType: 'SILVER',
           price: 40,
@@ -414,6 +421,14 @@ describe('MerchantPageComponent', () => {
     );
     expect(row.textContent).toContain('Requires Border Watch Reputation 25');
     expect(row.textContent).toContain('Current: 14');
+    // Once, not twice: slice §5's worked example shows the capacity line a
+    // single time.
+    expect(
+      countOccurrences(row.textContent, 'Capacity: 5 Raider Trophies'),
+    ).toBe(1);
+    // An empty description renders nothing at all, rather than an empty span
+    // that would let a duplicated capacity line back in unnoticed.
+    expect(row.querySelector('.shop-row__description')).toBeNull();
     expect(row.querySelector('button').disabled).toBe(true);
   });