[FEA] Allow all inactive in DEFAULT MODE.

#### SHM file

```yaml
# system modes example
---

actuation:
ros__parameters:
type: system
parts:
drive_base
left/manipulator
right/manipulator
modes:
__DEFAULT__:
drive_base: inactive.__DEFAULT__
left/manipulator: inactive.__DEFAULT__
right/manipulator: inactive.__DEFAULT__
LEFT:
# drive_base: active.__DEFAULT__
left/manipulator: active.__DEFAULT__
# right/manipulsator: inactive.__DEFAULT__
RIGHT:
# drive_base: active.__DEFAULT__
# left/manipulator: inactive.__DEFAULT__
right/manipulator: active.__DEFAULT__

left/manipulator:
ros__parameters:
type: node
modes:
__DEFAULT__:
ros__parameters:
max_torque: 0.1

drive_base:
ros__parameters:
type: node
modes:
__DEFAULT__:
ros__parameters:
max_speed: 0.1
controller: PID

right/manipulator:
ros__parameters:
type: node
modes:
__DEFAULT__:
ros__parameters:
max_torque: 0.11

```

#### step to reproduce

```sh
zs@zs-vm-2204:~/zs_ws/ga_ros$ time ros2 service call /actuation/change_state lifecycle_msgs/ChangeState "{transition: {id: 1, label: configure}}"
waiting for service to become available...
requester: making request: lifecycle_msgs.srv.ChangeState_Request(transition=lifecycle_msgs.msg.Transition(id=1, label='configure'))

response:
lifecycle_msgs.srv.ChangeState_Response(success=True)

real 0m2.185s
user 0m0.459s
sys 0m0.086s
```

#### expected behavior

all nodes would be in DEFAULT mode, which is all inactivated

#### actual behavior


Start with the ROS 2 service entry point /actuation/change_state and reproduce the configure request using the YAML system-modes example. Trace how the __DEFAULT__ mode assignments are applied, then verify that configuring /actuation leaves drive_base and both manipulators inactive.

Written by the indexing model from the issue text.