CAT-BG1: mesh-build-go publishes a done archive through oci-artifact-registry's verbs

Design 51: only a registry seat's holder writes into its store. The module pushed each bundle
and archive straight into the artifact store; it now publishes through the seat's publish and
publish-part with mesh-sdk's sender, invokes both verbs, and no longer requires artifact-store
or places its address. push.go is gone.

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

modules/mesh-build-go/module.json

@@ -67,12 +67,15 @@
     "forge-account",
     "go-toolchain",
     "go-package-registry",
-    "artifact-store",
     "node-tools"
   ],
   "binds": {
     "go-package-registry": "${dir:state}/go-package-registry.json"
   },
+  "invokes": [
+    "seat:oci-artifact-registry.publish",
+    "seat:oci-artifact-registry.publish-part"
+  ],
   "own-secrets": {
     "broker": "${dir:state}/broker"
   },
@@ -160,14 +163,6 @@
       "mode": "0644",
       "template": "files/gitconfig"
     },
-    {
-      "id": "registry",
-      "type": "file",
-      "path": "${dir:state}/registry",
-      "owner": "mesh-build-go",
-      "mode": "0644",
-      "template": "files/registry"
-    },
     {
       "id": "git",
       "type": "package",