Wire Tier 2 (interim) briefing trigger to document extraction pipeline

[AndreRobitaille]

Context

The TopicBriefing three-tier generation pipeline (issue #64) was implemented in commits a591132..828acbe. Tier 1 (headline_only) and Tier 3 (full) triggers are wired, but Tier 2 (interim) is not.

What exists

• Topics::UpdateTopicBriefingJob supports tier: "interim" and the code path works
• Ai::OpenAiService#generate_briefing_interim exists and uses gpt-5-mini (no temperature)
• The interim tier updates the headline and appends an upcoming note to editorial_content

What's missing

No pipeline event calls UpdateTopicBriefingJob with tier: "interim". Per the architecture design (docs/plans/2026-02-21-topic-briefing-architecture-design.md), this should fire when:

Document extraction completes, meeting has no minutes yet

This likely means adding a trigger after ExtractTopicsJob or document text extraction completes, checking that the meeting doesn't yet have minutes, and enqueuing:

Topics::UpdateTopicBriefingJob.perform_later(
  topic_id: topic.id,
  meeting_id: meeting.id,
  tier: "interim"
)

Files

• app/jobs/topics/update_topic_briefing_job.rb — the job (ready)
• app/services/ai/open_ai_service.rb — generate_briefing_interim method (ready)
• Trigger location TBD (likely ExtractTopicsJob or a document processing job)