Run the production Vault as three raft nodes on exch and infra-gamma

Two nodes on exch and one on infra-gamma, plain Compose per server, ports
on the private addresses only. Nodes unseal through the transit seal on the
platform Vault; the transit token reaches only the server process.

make prod-images resolves the latest stable Vault release once and pins its
digest in ignored .local/prod/images.env, so every node runs the same build.

infra/prod/README.md records the layout, the first rollout, node
replacement and recovery when the platform Vault is lost (#74).

infra/local/scripts/dispatch.sh

@@ -5,6 +5,7 @@ set -o pipefail
 . infra/local/scripts/secrets.sh
 case "${1:-}" in
  images) . infra/local/scripts/images.sh; images;;
+ prod-images) TOOL_STATE="$PWD/.local"; . infra/local/scripts/images.sh; prod_images;;
  up) . infra/local/scripts/bootstrap.sh; up;;
  email) . infra/local/scripts/bootstrap.sh; email;;
  sendico) . infra/local/scripts/bootstrap.sh; . infra/local/scripts/sendico.sh; configure_sendico;;

infra/local/scripts/images.sh

@@ -22,3 +22,10 @@ images() (
  cat "$WORK/images.env" | write "$STATE/images.env"
  cat "$STATE/images.env"
 )
+# Production pins: one resolution for every node of a cluster, so all of them
+# run the same build. Written outside .local/dev; copied to the servers.
+prod_images() (
+ ref=$(image hashicorp/vault latest) || exit 1
+ printf 'VAULT_IMAGE=%s\n' "$ref" | write "$PWD/.local/prod/images.env"
+ cat "$PWD/.local/prod/images.env"
+)

infra/local/scripts/test.sh

@@ -3,7 +3,7 @@ set -eu
 set -o pipefail
 # Shell syntax and static analysis cover the actual container shell scripts.
 shellcheck -s ash -x -S warning infra/local/scripts/dispatch.sh infra/local/scripts/test.sh
-shellcheck -x -S warning infra/local/tools.sh infra/local/scripts/start-service.sh infra/local/mongo/start.sh infra/local/nats/start.sh infra/local/vault/start.sh
+shellcheck -x -S warning infra/local/tools.sh infra/local/scripts/start-service.sh infra/local/mongo/start.sh infra/local/nats/start.sh infra/local/vault/start.sh infra/prod/vault/start.sh
 shellcheck -s ash -x -S warning infra/local/sendico/session.sh infra/local/sendico/check.sh infra/local/sendico/network.sh
 . infra/local/scripts/common.sh
 . infra/local/scripts/images.sh