feat: add cockpit triage backend foundation (Phase 1)
- Migration 071: add client_name, asset_name, issue_category,
triage_hypothesis, evidence_items columns to ai_sessions
- TriageUpdate schema for AI-inferred header updates in chat responses
- QuestionItem.options field for quick-reply buttons
- PATCH /ai-sessions/{id}/triage endpoint for manual header edits
- POST /ai-sessions/{id}/handoff-draft streaming endpoint for conclude modal
- Structured handoff fields (root_cause, steps_taken, recommendations)
on resolve/escalate requests, passed through to ResolutionOutputGenerator
- Triage fields exposed in AISessionDetail response for session resume
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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