Late control queue registration breaks message priority

### Feature Summary

When a new priority group belongs before an existing group, LinkedBlockingMultiQueue appends it instead of inserting it at the discovered position. A control queue registered after a data queue can therefore run after lower-priority data.

Before: register priority 2 then priority 1 -> stored order 2, 1 -> data selected first

After: register priority 2 then priority 1 -> stored order 1, 2 -> control selected first

Reproduction evidence:

Register a data subqueue with priority 2, then a control subqueue with priority 1. Put one message in each and read the first message.

Version and commit evidence:

1.3.0-incubating-SNAPSHOT (main)

**Commit Hash**

70c21145887920528d7d5540e3fb790b43e8b759

**What browsers are you seeing the problem on?**

Not browser-specific.

**Relevant log output**

```text
priority_order= [2, 1]
first_message= data message
second_message= control message
```

### Proposed Solution or Design

After: register priority 2 then priority 1 -> stored order 1, 2 -> control selected first

### Affected Area

Workflow Engine (Amber)