Real ExAthena.Providers.ClaudeCode.ModelSource backed by the claude_code SDK.
The CLI reports its supported models through the control-protocol initialize
handshake, which completes asynchronously after the session starts. We open a
short-lived session, poll ClaudeCode.Session.supported_models/1 until the
handshake lands (or a deadline passes), then stop the session. No query is
issued, and the session runs in :plan mode so it never touches the workspace.