docs: repoint a Design marker at the summary that outlives the spec

plan/spec-rfc7606-5-1-2-relay-shape.md was deleted at closure, per the
two-commit spec-closure rule, leaving the Design marker in
rfc7606_shape.go pointing at nothing. make ze-doc-links reported it as
the tree's one broken corpus reference.

Repointed at plan/learned/1225-rfc7606-relay-shape.md, the summary for
that same spec, which closure does not delete. That is the established
convention: cmd/ze-installer/main.go and cmd/ze/ze_core_autoinit.go
already cite learned summaries from their Design markers.

291 Go files cite a plan/spec- path, so every future closure orphans
whatever cites it. Nothing checks inbound references before a spec is
deleted. That class is named in plan/learned/1359, not fixed here.

Author: thomas-mangin

ai/DOCS-TO-CODE.md

@@ -2709,6 +2709,10 @@ Total: 306 design docs, 3256 files
 | `internal/component/ssh/passwordauth.go` | hash-as-token is local-only |
 | `internal/core/redact/redact.go` | credential-token redaction for logs |
 
+## `plan/learned/1225-rfc7606-relay-shape.md`
+
+- `internal/component/bgp/message/rfc7606_shape.go` -- one NLRI-bearing field per UPDATE
+
 ## `plan/learned/1226-test-health-dashboard.md`
 
 - `scripts/checks/inert_tests.go` -- test-sensitivity ratchet
@@ -4481,10 +4485,6 @@ Total: 306 design docs, 3256 files
 | `internal/component/web/server_tls_test.go` | web TLS chain + rotation tests |
 | `internal/core/dnsserver/secure_pki_test.go` | DoT/DoH PKI certificate reference tests |
 
-## `plan/spec-rfc7606-5-1-2-relay-shape.md`
-
-- `internal/component/bgp/message/rfc7606_shape.go` -- one NLRI-bearing field per UPDATE
-
 ## `plan/spec-unify-filters.md`
 
 - `internal/component/bgp/reactor/unified_filter_order_test.go` -- unified stage-ordered filter pipeline

internal/component/bgp/message/rfc7606_shape.go

@@ -1,4 +1,4 @@
-// Design: plan/spec-rfc7606-5-1-2-relay-shape.md -- one NLRI-bearing field per UPDATE
+// Design: plan/learned/1225-rfc7606-relay-shape.md -- one NLRI-bearing field per UPDATE
 // RFC: rfc/short/rfc7606.md -- Section 5.1 second bullet (sender-side encoding restriction)
 // Related: update_split.go -- Splitter.SplitCompliant, the enforcement point for parsed UPDATEs
 // Related: ../wireu/split.go -- SplitWireUpdate, the enforcement point for wire UPDATEs