CAT-D6: distribution's health is a tool the runtime runs outside the program, asking versions through the store's read side

An http probe of /v2/ said only that a port answered; design 51 asks the health check to call versions per seat and
probe the read side each minute, naming the program when it is down, from outside its process. registry_health asks
versions of each seat through the program's port, writes the read-side finding while it fails and clears it after.

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

modules/distribution/module.json

@@ -44,6 +44,7 @@
   ],
   "tools": [
     "registry_direct_writes",
+    "registry_health",
     "registry_holds",
     "registry_incoming",
     "registry_old_name"
@@ -198,8 +199,12 @@
       },
       "user": "distribution",
       "health": {
-        "kind": "http",
-        "url": "http://127.0.0.1:5000/v2/"
+        "kind": "tool",
+        "tool": "registry_health",
+        "interval": "60s",
+        "timeout": "10s",
+        "looks": 2,
+        "grace": "90s"
       }
     },
     {