docs(archreview): add STATUS.md handoff + per-plan status banners

Track remediation progress: 2 of 4 Criticals done (03/S1 split-brain resolver;
02/U2+U3 VT timeout+ALC) + both CLAUDE.md doc-drifts fixed. STATUS.md is the
single source of truth (branch topology, completed items, task list, next-up,
resume facts). Each plan carries a status banner.

archreview/plans/03-server-runtime-plan.md

@@ -1,5 +1,11 @@
 # Design & Implementation Plan — Server & Runtime Subsystem (Report 03)
 
+> **Status (2026-07-08):** ✅ **S1 (Critical) activation DONE** — branch `fix/archreview-crit1-split-brain-resolver`
+> @ `a81dea10` (typed `KeepOldestOption`, unit guards + e2e config-resolution verified). ✅ **U1 doc DONE**
+> (CLAUDE.md KNOWN LIMITATION 2 corrected). ⬜ S1's hard-kill failover **integration test** still pending (task 9,
+> effort-M). ⬜ **U2 (reflection forwarding test) pending — MUST land before P1 surgical-adds** / any new sink
+> capability. Remaining: P1, S2/S3/S4. See [`STATUS.md`](STATUS.md).
+
 - **Source report:** `archreview/03-server-runtime.md`
 - **Review commit:** `9cad9ed0`
 - **Verification pass performed against tree at:** current `master` (same tree; all cited files present)