perf: memo GridCard, fuse save fns, fix slash tab active color

memento-note/tests/unit/brainstorm-billing.test.ts

@@ -117,6 +117,23 @@ describe('brainstorm host-pays billing (Story 3.4)', () => {
         checkSessionEntitlementOrThrow('host-1', 'guest-9', true, 'brainstorm_expand'),
       ).rejects.toThrow()
     })
+
+    it('AC10: host BYOK + guest quota empty still bills host (guest has no quota, host pays)', async () => {
+      vi.mocked(hasAnyActiveByok).mockResolvedValue(true)
+      mockActiveSubscription('PRO')
+      vi.mocked(redis.eval).mockResolvedValue(1)
+
+      // Guest's quota is empty (simulated by checking guest's quota returns 0)
+      vi.mocked(redis.get).mockResolvedValue('0')
+
+      await checkSessionEntitlementOrThrow('host-1', 'guest-9', true, 'brainstorm_expand')
+
+      // Verify that host's redis key was incremented, not guest's
+      expect(redis.eval).toHaveBeenCalled()
+      const keyArg = String(vi.mocked(redis.eval).mock.calls[0]?.[2])
+      expect(keyArg).toContain('host-1')
+      expect(keyArg).not.toContain('guest-9')
+    })
   })
 
   describe('QuotaExceededError.toJSON', () => {