share_url is the fully-qualified URL of this run's public view, rooted at the
deployment's LangSmith app origin (for example
https://smith.langchain.com/public/4f7a1b2c-8d9e-4a0b-9c1d-2e3f4a5b6c7d/r). It
is returned only when SHARE_URL is included in selects, and only when the
run has been explicitly shared; the URL remains stable until the run is
unshared. Anyone with this URL can view the run anonymously, so treat it as a
secret and do not log it.
