Declare what hello-web is made of, to prove a build from a path

A proof branch, not for main: the route-forwarding bed reads this module's literal
image and would break until the module is built.

The modelling is right regardless — the image is upstream, so the mesh should
mirror it once into its own registry and pin what that registry assigned, rather
than every machine fetching a reference somebody else can move.

Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx

modules/hello-web/module.json

@@ -48,7 +48,6 @@
       "id": "server",
       "type": "container",
       "name": "hello-web",
-      "image": "alpine@sha256:28bd5fe8b56d1bd048e5babf5b10710ebe0bae67db86916198a6eec434943f8b",
       "network": "hello-web",
       "ports": [
         "8080:8080"
@@ -60,7 +59,17 @@
         "sh",
         "-c",
         "while true; do { printf 'HTTP/1.1 200 OK\\r\\nContent-Type: text/plain\\r\\nConnection: close\\r\\n\\r\\n'; cat /www/index.html; } | nc -l -p 8080; done"
-      ]
+      ],
+      "artifact": "server"
     }
-  ]
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "server",
+        "kind": "upstream",
+        "from": "alpine@sha256:28bd5fe8b56d1bd048e5babf5b10710ebe0bae67db86916198a6eec434943f8b"
+      }
+    ]
+  }
 }