docs(backlog): track multi-context e2e gap from TEST-INFRA-001 cut #4

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dev-docs/BACKLOG.md

@@ -2543,6 +2543,9 @@ contract test) but no automated gate prevents drift over time.
   via `make test-db-create` then `migrate:fresh + seed` from
   globalSetup. No state shared across runs (unlike local
   development).
+- Multi-browser-context e2e patterns for optimistic locking flows
+  with UI rollback validation in the second context (cut #4 from
+  TEST-INFRA-001 sprint)
 
 **Trigger:** No explicit deadline. Surfaces when first review cycle
 feels drift without automated tests, OR when first regression slips