weichen
67cf52bb77
Why: cardflow-r1 deferred three capabilities (card content streaming, artifact unification, cross-session inbox CF3); user directed 2026-09-30 to implement them, plan first. Evidence: code survey at Dev R0=d64742c (cardsvc.Update streaming base, artifact_ref ctxasm gap, activity_cards project_id column reserved). Impact: reviewable proposal D44-D52 with three-phase task split; no runtime behavior change yet. Refs: 2026-09-30-cardflow-and-process-split.md (D39-D43).