fix(eks): propagate nodegroup DiskSize to worker root volume

launchWorkers built RunInstancesInput with no BlockDeviceMappings, so
parseVolumeParams applied the 4GB root-volume default and the nodegroup
DiskSize was silently ignored. Wire rec.DiskSize into a BlockDeviceMapping
when set.

spinifex/handlers/eks/nodegroup.go

@@ -327,6 +327,12 @@ func (s *EKSServiceImpl) launchWorkers(accountID string, rec *NodegroupRecord, m
 				},
 			}},
 		}
+		if rec.DiskSize > 0 {
+			runInput.BlockDeviceMappings = []*ec2.BlockDeviceMapping{{
+				DeviceName: aws.String("/dev/vda"),
+				Ebs:        &ec2.EbsBlockDevice{VolumeSize: aws.Int64(rec.DiskSize)},
+			}}
+		}
 		res, err := s.deps.Worker.RunWorkerInstance(runInput, accountID)
 		if err != nil {
 			return ids, fmt.Errorf("run worker %d/%d: %w", i+1, count, err)

spinifex/handlers/eks/nodegroup_test.go

@@ -213,6 +213,34 @@ func TestCreateNodegroup_HappyPath(t *testing.T) {
 	require.EqualError(t, err, awserrors.ErrorEKSResourceInUse)
 }
 
+func TestCreateNodegroup_DiskSizePropagatesToBlockDeviceMapping(t *testing.T) {
+	f := newEKSServiceFixture(t)
+	seedActiveClusterWithToken(t, f, "c1")
+
+	in := createNGInput("c1", "ng1", 1)
+	in.DiskSize = aws.Int64(30)
+	_, err := f.svc.CreateNodegroup(in, testAccountID)
+	require.NoError(t, err)
+
+	require.Len(t, f.worker.runCalls, 1)
+	bdm := f.worker.runCalls[0].BlockDeviceMappings
+	require.Len(t, bdm, 1)
+	require.NotNil(t, bdm[0].Ebs)
+	assert.Equal(t, int64(30), aws.Int64Value(bdm[0].Ebs.VolumeSize))
+}
+
+func TestCreateNodegroup_NoDiskSizeOmitsBlockDeviceMapping(t *testing.T) {
+	f := newEKSServiceFixture(t)
+	seedActiveClusterWithToken(t, f, "c1")
+
+	_, err := f.svc.CreateNodegroup(createNGInput("c1", "ng1", 1), testAccountID)
+	require.NoError(t, err)
+
+	require.Len(t, f.worker.runCalls, 1)
+	// No DiskSize requested → leave the launch path on its default sizing.
+	assert.Empty(t, f.worker.runCalls[0].BlockDeviceMappings)
+}
+
 func TestCreateNodegroup_ClusterNotActive(t *testing.T) {
 	f := newEKSServiceFixture(t)
 	require.NoError(t, PutClusterMeta(f.kv, &ClusterMeta{