Unblock: td-da61c1 architecture track status and close criteria

**Why this matters:** td-da61c1 is a P1 onboarding architecture ticket with no visible status updates since 2026-03-29 despite being part of the active onboarding redesign path. Stale state risks duplicated effort and unclear ownership on implementation closure.\n\n**Scope:** Reconcile what is already shipped vs still pending in the architecture/knowledge-doc track, define explicit close criteria for td-da61c1, and identify whether residual work should be split into new child tasks.\n\n**Source signal:** td-da61c1 handoff/state age; onboarding redesign remains the primary referral lever.