archetypes: build an archetype agent from its archetype's module on the hive

The hive reads the agent-archetype key when it provisions and rebuilds an
agent and keeps it in swarm-agent-archetypes.json. For an archetype agent
the meta flake has no agent-<name> input and mkAgent imports
hyperhive.hyperhiveArchetypes.<name>.module; provisioning, rebuilds, the
meta-input cascade, a deploy's rev and the startup migration skip the
config repos. The harness gets HIVE_ARCHETYPE and the system prompt says
the agent has no config repo. The create form sends the picked archetype.
Adds the android-dev built-in.

Refs #5386

nix/archetypes/default.nix

@@ -17,4 +17,18 @@
       ];
     };
   };
+  android-dev = {
+    module =
+      { pkgs, ... }:
+      {
+        environment.systemPackages = [
+          pkgs.android-tools
+          pkgs.gradle
+          pkgs.jdk
+        ];
+      };
+    meta = {
+      description = "Builds Android apps: adb and fastboot (android-tools), Gradle and a JDK are installed. It holds the default permissions.";
+    };
+  };
 }