Survey the machine, and say what an install would do to it

The first two pieces of the installer, and deliberately the two that change
nothing: what this machine is, and what would happen to it.

The survey is the floor under every later choice -- a component can only
offer a container shape if Docker answers for this user, or a host shape on
a systemd machine with what that shape needs. It reports what it could not
establish as unknown rather than guessing: an unprivileged probe of port 25
means "I may not bind this", not "something is listening", and reporting
the first as the second is a lie an operator would act on.

The plan is one list, and it will have three readers: --dry-run prints it,
the interface will show it before anything happens, and apply will walk it.
What you are shown is what runs.

Tested on a fresh Debian 13 in qemu, which has neither Docker nor Node and
so exercises every unavailable shape: 23 checks, including that nothing was
created by any of it. The lab that machine runs in is in e2e/vm.

e2e/cases/survey.sh

@@ -0,0 +1,66 @@
+#!/bin/bash
+# SPDX-FileCopyrightText: 2026 Coffey Labs
+# SPDX-License-Identifier: AGPL-3.0-or-later
+#
+# The first case: on a machine with nothing installed on it, does the
+# installer describe that machine correctly, and does it refuse the shapes
+# that machine cannot do -- with a reason someone could act on?
+#
+# A fresh Debian cloud image has no docker and no node, which is exactly the
+# interesting case: every container shape and the webmail's host shape are
+# unavailable, and the server's host shape is not. Getting this wrong in
+# either direction is the difference between an installer that reads a
+# machine and one that guesses.
+#
+# Run from the host with: e2e/vm/run.sh e2e/cases/survey.sh
+set -uo pipefail
+
+pass=0; fail=0
+ok()   { echo "  ok   $*"; pass=$((pass+1)); }
+bad()  { echo "  FAIL $*"; fail=$((fail+1)); }
+has()  { grep -q -- "$2" <<<"$1" && ok "$3" || { bad "$3"; echo "----"; echo "$1" | sed 's/^/    /'; echo "----"; }; }
+hasnt() { grep -q -- "$2" <<<"$1" && { bad "$3"; } || ok "$3"; }
+
+echo "==> survey, on a machine with nothing on it"
+S="$(/tmp/inbuxa survey)"
+echo "$S" | sed 's/^/    /'
+
+has "$S" "Debian GNU/Linux 13" "names the distribution"
+has "$S" "init                   systemd" "sees systemd"
+has "$S" "running as             root" "knows it is root"
+has "$S" "docker                 not installed" "sees no docker"
+has "$S" "node                   not installed" "sees no node"
+has "$S" "25     SMTP" "lists the mail ports"
+hasnt "$S" "cannot tell without root" "as root, every port is a real answer"
+has "$S" "container (no: docker is not installed)" "containers unavailable, with the reason"
+has "$S" "server     container (no" "the server cannot be a container here"
+has "$S" "webmail    container (no: docker is not installed)   host (no: a host install of the webmail needs Node 22" "the webmail can be neither shape here"
+
+echo
+echo "==> a plan that this machine cannot carry out"
+OUT="$(/tmp/inbuxa install --domain example.test 2>&1)"; rc=$?
+[ $rc -ne 0 ] && ok "refuses (exit $rc)" || bad "should have refused"
+has "$OUT" "cannot install as asked" "says so plainly"
+has "$OUT" "docker is not installed" "and why"
+
+echo
+echo "==> a plan it can: the server on the host, front ends elsewhere"
+OUT="$(/tmp/inbuxa install --domain example.test --server host --console skip --webmail skip --dry-run 2>&1)"; rc=$?
+echo "$OUT" | sed 's/^/    /'
+[ $rc -eq 0 ] && ok "accepted (exit 0)" || bad "should have been accepted, exit $rc"
+has "$OUT" "/etc/systemd/system/inbuxa-server.service" "names the unit it would write"
+has "$OUT" "user: inbuxa" "names the user it would create"
+has "$OUT" "Ports it will bind: 25, 465, 993, 995, 4190, 80, 443" "lists every port"
+has "$OUT" "MX    10 mail.example.test." "writes the MX the domain needs"
+has "$OUT" "_dmarc.example.test." "and DMARC"
+hasnt "$OUT" "admin.example.test" "says nothing about front ends it was told to skip"
+
+echo
+echo "==> nothing was installed by any of that"
+[ ! -e /etc/systemd/system/inbuxa-server.service ] && ok "no unit written" || bad "a unit appeared"
+[ ! -e /var/lib/inbuxa ] && ok "no deployment directory" || bad "a directory appeared"
+id inbuxa >/dev/null 2>&1 && bad "a user appeared" || ok "no user created"
+
+echo
+echo "==> $pass passed, $fail failed"
+[ "$fail" -eq 0 ]