feat: implement WP-0002 — Goss test suite, verify playbook, and ADR-002

- goss/baseline.yaml: assertions for all spec/server-baseline.yaml items
  (packages, services, SSH config, UFW rules, admin user, fail2ban, HISTCONTROL)
- goss/vars/baseline-vars.yaml: parameterised ports and paths
- ansible/roles/goss/: installs Goss binary (v0.4.9), deploys tests,
  runs assertions in TAP format, fetches report to reports/
- ansible/playbooks/verify.yaml: playbook wrapping the goss role
- Makefile: add 'make verify' target; update 'make status' with hint
- docs/adr/ADR-002: formal repo boundary — railiance-hosts vs railiance-bootstrap
- workplans/RAIL-HO-WP-0002: registered workstream 8fed53c2, T03–T06 done

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

goss/vars/baseline-vars.yaml

@@ -0,0 +1,11 @@
+# Parameterised values used in goss/baseline.yaml
+# Override per host group if defaults differ.
+
+firewall_ports:
+  ssh: "22/tcp"
+  k3s_api: "6443/tcp"
+  flannel_vxlan: "8472/udp"
+
+admin_user: admin
+goss_binary: /usr/local/bin/goss
+goss_tests_dir: /etc/goss