Run user interview

1. Context: list_workspaces(), list_projects(workspace_id).
2. Create: create_interview(workspace_id, project_id, name, target_url, research_brief?). target_url is where participants land; the brief is 1 to 3 paragraphs on what you want to learn and what it informs.
3. Guide: add_interview_section(interview_id, title, intro_script?), then 2 to 5 items each via add_interview_item(section_id, type, prompt_text, expected_evidence?). type: "task" has the participant act in the browser; "question" is an open-ended answer. Tasks beat questions for journey research; use questions for reactions and "why". Keep to 1 to 3 sections and about 15 items at most.
4. Participants: add_interview_participant(interview_id, …) with an actor_id (from list_actors, see create-actor-panel) or a persona_spec (name, bio, 3 to 5 traits). Use 3 to 5, varying segment, device and locale.
5. Launch: launch_interview(interview_id) is async; participants run in parallel.
6. Watch: get_interview(interview_id) shows each participant's status (pending, running, completed, failed). get_interview_participant(participant_id) returns the full transcript with actions.
7. Report: once all participants land, get_interview_report(interview_id) returns { summary, themes, recommendations, per_question_rollup }. After changing participants or fixing a failed one, regenerate_interview_report(interview_id). Retry failed participants (dashboard) before regenerating.