registerScriptExtensions

Teach the session the same script shape the compiler uses, so a snippet's implicit ScriptScope receiver and its bare Patches / Probe imports resolve here too. McpScriptRegistrar is reused as-is: the relocated Analysis API and the embedded compiler share one FirExtensionRegistrar class.

LLFirSessionFactory reads this extension point with no null guard, so the point has to exist before the first session is configured — standalone does not register this one itself. Scoped to owner, which is the session's own disposable: the unscoped overload is deprecated, and rightly so.