Get Interview Join Info

Public endpoint — no auth required. Returns LiveKit connection info, finding-or-creating the right session under this interview.

This is the canonical user-facing entry point for join links. The interview ID is the stable identifier for the conversation across multiple sessions and revisions; sessions are minted on demand.

Branches (delegated to sessions._join_for_interview):

• Live session present → return it.
• Last session completed, interview in_progress → spawn continuation with restored committed_goal_state + transcript tail + summary.
• Interview processing/processing_failed → 409 (transient).
• Interview completed → 410 unless the template has settings.allow_re_completion = true, in which case it re-opens and increments the revision counter.