Add the first-node scenario

One machine with PostgreSQL in its registry, for developing the bootstrap.
Used to verify that a sealed machine can raise a store and a database from the
bundle its host carries.

scenarios/first-node.yml

@@ -0,0 +1,22 @@
+# One machine, raising a substrate from the bundle its host carries.
+#
+# This is the bootstrap class (novox/hq ADR 0009): no forge, no control plane, no delivery. It
+# exists to develop the first three steps of raising a mesh — a container runtime, a store, and
+# a database inside it — which is as far as the bootstrap can go until a control plane exists.
+scenario: first-node
+
+segments:
+  hosting:
+    kind: public
+    cidr: [192.0.2.0/24]
+
+machines:
+  anchor:
+    at: { segment: hosting, address: [192.0.2.10] }
+    inbound: allow
+
+images:
+  - postgres:17-alpine
+
+place:
+  all: [host, runtime]