Intent of restore round-trip changeModel on a peer chat refreshes its backing and fires onDidChangeChatData|occurrence=1

All 1 exact test in this concept. Every test is marked by where it enters the hierarchy.

mocha:v1|namespace=vscode@05c208e9e28d8c1c723fa08f85e2b7a96092e8e5|file=vs/ 1 test
- platform/ 1 test
  - agentHost/ 1 test
    
    test/ 1 test
    
    node/ 1 test
    
    copilotAgent.test|title=CopilotAgent peer chat create / 1 test
    
    fork / 1 test
    
    model+agent / 1 test
    
    mocha:v1|namespace=vscode@05c208e9e28d8c1c723fa08f85e2b7a96092e8e5|file=vs/platform/agentHost/test/node/copilotAgent.test|title=CopilotAgent peer chat create / fork / model+agent / restore round-trip changeModel on a peer chat refreshes its backing and fires onDidChangeChatData|occurrence=1 Introduced here