ADR-004: back out of on-stack RAP; retarget to starter customizing tenant

Both tenants belong to the same starter system: my429480 is its
customizing tenant (client 100, key-user extensibility only, no ABAP)
and my431353 is its development tenant (client 080). This package had
recorded my429480 as "productive" and ADR-002 had assumed it offered
developer extensibility; both were wrong.

- ADR-004 withdraws the on-stack RAP route and moves the application to
  a side-by-side runtime against released OData APIs. ADR-002 marked
  superseded.
- Development tenant my431353 parked: all 19 ZARENA_PLM objects left
  active, sources kept in docs/handover/rap/ as reference, so the route
  stays reversible.
- Replacement host left open as OQ-11 (key-user extensibility vs CAP
  side-by-side); recommendation recorded as CAP. No build starts until
  OQ-11 is closed.
- RAP-dependent items V-2, V-3, OQ-5, OQ-8, OQ-9, OQ-10 parked rather
  than closed.
- Tenant references corrected across CLAUDE.md, KNOWLEDGE.md,
  app/README.md, the RAP handover README, the rap-developer agent and
  the reentrance-login helper README.

No SAP tenant was modified.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/adr/ADR-002-on-stack-first.md

@@ -1,6 +1,13 @@
 # ADR-002 — On-stack first: RAP approval domain + Fiori app in the tenant; side-by-side reduced to a connectivity worker
 
-Date: 2026-09-04 · Status: Accepted (amends ADR-001)
+Date: 2026-09-04 · Status: **Superseded by ADR-004 (2026-09-29)** (amended ADR-001)
+
+> **Superseded 2026-09-29.** The customizing tenant `my429480` (client 100)
+> supports key-user extensibility only, so the RAP business object below has
+> no home there; `my429480` and `my431353` are the starter system's
+> customizing and development tenants, not a development and a productive
+> system. V-1 below, "confirm developer-extensibility access on my429480",
+> was unanswerable as written. See ADR-004.
 
 ## Context