Offer only what this machine can deliver

The installer knew one distribution: Debian, with docker, on a new enough
release. Everything else it would have offered and then failed at.

Three facts now decide what the matrix offers, and each is read from the
machine rather than assumed:

- The container runtime. Docker where the machine has one, podman on the Red
  Hat family, which ships no docker at all. Both go through the same compose
  plugin: compose speaks the Docker API and podman serves it, so there is one
  compose file and one deployment path, not two. Telling a Fedora operator to
  add Docker's own repository to a machine that already has a container
  runtime would have been the wrong trade.

- glibc. The server binary is downloaded, not built here, and it is linked
  against 2.39. Rocky 9 (2.34), Debian 12 and Ubuntu 22.04 cannot run it, so
  the host shape is refused there with the version found and the container
  shape named as the answer -- rather than installing a file that cannot
  start.

- The operating system itself. This compiles for macOS and Windows because Go
  compiles anything, and on either it would read no os-release, find no
  systemd, and describe a machine that does not exist. It now says what it is
  and exits.

Two bugs the other distributions found, both of which Debian could not have:

- The survey reported the first thing in the way and stopped, so on Fedora it
  asked to start podman.socket, and then -- having done it -- asked for the
  compose plugin. Needs are named now, not described, and reported together.

- apply used the survey taken before dependencies were installed, so on a
  machine that had no runtime at all it installed podman and then reached for
  docker. It re-surveys after resolving, and stops if containers still are
  not usable.

The lab takes DISTRO now: debian13, debian12, ubuntu2404, fedora, rocky9,
arch, each with its own disk and ssh port so several can be up at once. The
cases no longer say "docker" either. install-local passes on Debian 13,
Fedora 43 and Rocky 9 -- 20 checks each, ending with a sign-in to the webmail
the installer put there.

e2e/cases/install-local.sh

@@ -21,6 +21,20 @@ has()  { grep -q -- "$2" <<<"$1" && ok "$3" || { bad "$3"; echo "$1" | tail -20
 
 DIR=/var/lib/inbuxa
 
+# Whichever runtime this machine has. The installer picks docker where there
+# is one and podman on the Red Hat family; a case that says "docker" only
+# tests half the distributions it is run on.
+if command -v docker >/dev/null 2>&1; then
+  RT=docker
+  compose() { docker compose -f "$DIR/compose.yaml" "$@"; }
+else
+  RT=podman
+  compose() {
+    DOCKER_HOST=unix:///run/podman/podman.sock \
+      /usr/local/lib/docker/cli-plugins/docker-compose -f "$DIR/compose.yaml" "$@"
+  }
+fi
+
 echo "==> installing"
 OUT="$(/tmp/inbuxa install --local --domain example.test --install-deps --yes 2>&1)"; rc=$?
 echo "$OUT" | grep -v '^    |' | tail -24 | sed 's/^/    /'
@@ -38,7 +52,7 @@ grep -q "_domainkey" "$DIR/dns.zone" && ok "and the DKIM key it generated" || ba
 
 echo
 echo "==> what it left running"
-STATE="$(docker compose -f $DIR/compose.yaml ps --format '{{.Service}} {{.State}}')"
+STATE="$(compose ps --format '{{.Service}} {{.State}}')"
 for s in server console webmail; do
   grep -q "^$s running" <<<"$STATE" && ok "$s is running" || { bad "$s is not running"; echo "$STATE" | sed 's/^/    /'; }
 done
@@ -52,7 +66,7 @@ curl -fsS http://127.0.0.1:8080/api/health 2>/dev/null | grep -q '"ok":true' &&
 
 echo
 echo "==> the bootstrap credential did not outlive the setup"
-ENVOUT="$(docker inspect --format '{{range .Config.Env}}{{println .}}{{end}}' "$(docker compose -f $DIR/compose.yaml ps -q server)")"
+ENVOUT="$($RT inspect --format '{{range .Config.Env}}{{println .}}{{end}}' "$(compose ps -q server)")"
 grep -q "RECOVERY_ADMIN" <<<"$ENVOUT" && { bad "the server still carries a recovery admin"; echo "$ENVOUT" | grep RECOVERY | sed 's/^/    /'; } || ok "no recovery admin in the running server"
 grep -q "INBUXA_WEBMAIL_CLIENT_SECRET" <<<"$ENVOUT" && ok "the webmail's client secret is where it belongs" || bad "the server has no webmail client secret"
 
@@ -70,7 +84,7 @@ grep -q "urn:ietf:params:jmap:mail" /tmp/login.json && ok "and the session carri
 echo
 echo "==> running it again converges rather than duplicating"
 OUT="$(/tmp/inbuxa install --local --domain example.test --yes 2>&1)"; rc=$?
-COUNT=$(docker compose -f $DIR/compose.yaml ps --format '{{.Service}}' | sort -u | wc -l)
+COUNT=$(compose ps --format '{{.Service}}' | sort -u | wc -l)
 [ "$COUNT" = 3 ] && ok "still three services, not six" || bad "$COUNT services after a second run"
 
 echo