general purpose agent used instead of actual agent

### Describe the bug

Sometimes it uses a "general purpose" agenet (recently added to copilot-cil) instead of an actual defined agent (that has been working just fine till this release with general purpose agents)

I have an architect agent, the instructions reference how to use it, it picked that up "let me
invoke the architect" but then goes and uses a general purpose agent. Sometimes that general purpose agent will read the actual agent file, sometimes not.

If there is an actual agent, it must be used

### Affected version

0.0.377 Commit: 4a0b36b

### Steps to reproduce the behavior

1. create an agent
2. tell it to use said agent
3. it uses a "general purpose" agent

### Expected behavior

If an agent file / config exists, it must be used.

### Additional context

_No response_