`preprovision` hook fails when provisioning COBO agent with new env

[JeffreyCA]

Repro steps:

1. In an already-initialized COBO project, create a new azd env: azd env new <name>
2. Run azd up

The preprovision hook fails during SetIdentity in parser.go:

ERROR: deployment failed: failed invoking event handlers for 'preprovision', extension azure.ai.agents project hook preprovision failed: failed to set identity: invalid resource ID format:

This can also arise if user is using a template where init was previously called and they've freshly cloned the repo and are trying to provision + deploy.