test(inventory): cover the non-equippable branch of the detail panel

The panel's three-way actions block had no test for its middle branch:
an item with equipmentSlot null should show "Nicht ausrüstbar" and no
equip button. The gap predates this slice -- Task 14's review found it
while confirming the removed level gate had not cost coverage.

Deferred until now on purpose: the web bundle could not compile for the
whole slice, so committing this earlier would have meant shipping a test
I had never executed.

Load-bearing: dropping the !isEquippable() guard would fall through to
the else branch and render the button, failing the assertion.

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

apps/web/src/app/features/inventory/inventory-detail-panel.component.spec.ts

@@ -37,6 +37,23 @@ const banditBlade: InventoryItem = {
   },
 };
 
+const ashPelt: InventoryItem = {
+  id: 'item-pelt',
+  quantity: 3,
+  equipped: false,
+  item: {
+    key: 'ash-pelt',
+    name: 'Aschenfell',
+    rarity: 'COMMON',
+    equipmentSlot: null,
+    weaponDamage: 0,
+    bonusAttack: 0,
+    bonusHp: 0,
+    bonusArmor: 0,
+    iconPath: '/images/items/ash-pelt.png',
+  },
+};
+
 async function setup(overrides: {
   item?: InventoryItem | null;
   equippedItemInSlot?: InventoryItem | null;
@@ -66,6 +83,15 @@ describe('InventoryDetailPanelComponent', () => {
     expect(element.querySelector('[data-detail-equip]')).toBeNull();
   });
 
+  it('refuses to offer an equip button for a non-equippable item', async () => {
+    const fixture = await setup({ item: ashPelt });
+    const element = fixture.nativeElement as HTMLElement;
+
+    expect(element.textContent).toContain('Nicht ausrüstbar');
+    expect(element.querySelector('[data-detail-equip]')).toBeNull();
+    expect(element.querySelector('[data-detail-equipped]')).toBeNull();
+  });
+
   it('shows the stat comparison against the equipped item in the same slot', async () => {
     const fixture = await setup({ item: banditBlade, equippedItemInSlot: wornSword });
     const text = (fixture.nativeElement as HTMLElement).querySelector('[data-detail-stats]')?.textContent ?? '';