distribution: the store's /v2/ checked over http through the front, beside the program's tool check (issue 1966)

A tool check alone is refused by the indexer's judge (ADR 0227 rule 8, ADR 0240 rule 2); the operator chose a check of
another kind on 2026-11-04.

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

modules/distribution/module.json

@@ -197,6 +197,16 @@
       ],
       "env": {
         "REGISTRY_STORAGE_DELETE_ENABLED": "true"
+      },
+      "health": {
+        "kind": "http",
+        "endpoint": "registry",
+        "path": "/v2/",
+        "status": 200,
+        "interval": "60s",
+        "timeout": "10s",
+        "looks": 2,
+        "grace": "90s"
       }
     },
     {