feat: add node-signed system body write admission

routing/public-navigation-anchor.json

@@ -1,7 +1,7 @@
 {
   "schema": "guanghu.public-navigation-anchor/v1",
   "anchor_id": "GLW-PUBLIC-NAV-ANCHOR-001",
-  "version": "2026-08-10.4",
+  "version": "2026-08-10.5",
   "state": "CURRENT_CANONICAL",
   "repository_id": "REPO-012",
   "branch": "main",
@@ -43,7 +43,7 @@
     "navigation": {
       "path": "routing/ai-machine-navigation-map.json",
       "id": "AI-MACHINE-NAV-001",
-      "version": "2026-08-10.3"
+      "version": "2026-08-10.4"
     },
     "lighthouse_paths": {
       "path": "routing/lighthouse-path-registry.json",