docs: add the registry as a product section on the hub (PROT-50)

docs-hub/intro.md

@@ -20,7 +20,11 @@ Protostar is built as a set of components, each developed in its own repository
 with its docs living next to the code. This site lifts those docs into one place:
 
 - **[CLI](/cli)** — the `protostar` command-line tool: a self-contained binary
-  you can run without installing the .NET runtime.
+  you can run without installing the .NET runtime. This is what you install and
+  run on your own machine.
+- **[Registry](/registry)** — the service the CLI syncs to: identity, the
+  versioned API, and (as the loop fills in) the home of the refinement engine.
+  Aimed at people who run, operate, or develop the service.
 
 More components will appear here as they land. Each one keeps its docs in its own
 repo; this hub aggregates them at build time.

docs.manifest.json

@@ -9,6 +9,15 @@
       "docsPath": "docs",
       "routeBasePath": "cli",
       "navbarPosition": "left"
+    },
+    {
+      "id": "protostar-registry",
+      "label": "Registry",
+      "repo": "voidprojectssoftware/protostar-registry",
+      "ref": "main",
+      "docsPath": "docs",
+      "routeBasePath": "registry",
+      "navbarPosition": "left"
     }
   ]
 }