Custom Agents list does not update after installing a plugin

[tlmii]

Describe the bug

When you install a plugin with a custom agent, the agent is not available until after a restart

Affected version

No response

Steps to reproduce the behavior

1. Install a plugin with an agent (e.g. /plugin install azure-cloud-development@awesome-copilot
2. Check the agents list with /agent
3. Note the new agents are not there
4. Restart copilot cli
5. Check the agents list with /agent
6. Note that you now get a bunch of warnings because its at least TRYING to load the agents (but you run into Agents installed from a plugin aren't loaded #1636 at that point)

Expected behavior

Agents are available for selection immediately

Additional context

No response