feat(info): show the install reason and drop the indentation

N? and `info PKG` now print three lines, none indented:

    PKG: <description>
    reason: explicitly installed | installed as a dependency | unknown | not installed
    required by: <installed dependents, comma separated> | nothing

The reason comes from a new <be>_reason backend function: apt-mark
showauto / showmanual (dpkg decides for a package in neither list), the
Install Reason of pacman -Qi, dnf repoquery --installed %{reason} (dnf4
and dnf5 words) and the Installed line of zypper info (rpm plus libzypp's
AutoInstalled when zypper is locked). A row whose old version is "-" is
not installed and the backend is not asked. The "(installed)" qualifier
moves to --help, README and DESIGN.

The rpm E2E fixture and e2e_reset now also mark su-dummy-a and su-dummy-c
as user-installed on dnf, which records plain rpm installs as "unknown",
so 1? and 2? show both reasons on all 12 distros. The verified commands
are recorded in discovery/{apt,pacman,rpm}.md.

tests/unit/fakes/apt/dpkg-query

@@ -2,7 +2,8 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 # Copyright (C) 2026 Bryan Joshua Pedini
 
-# fake dpkg-query (unit tests): the dpkg database dump used for dependency closures
+# fake dpkg-query (unit tests): the dpkg database dump used for dependency closures, and
+# `-W -f '${db:Status-Abbrev}' NAME` (the status of one package; purged = unknown to dpkg)
 # shellcheck source=../fakelib.bash
 . "${BASH_SOURCE[0]%/*}/../fakelib.bash"
 fake_log "$@"
@@ -10,7 +11,30 @@ fake_log "$@"
 st=${SKEPTICAL_UPDATER_STATE_DIR:-}/trusted.tsv
 if [[ -n ${FAKE_STATE_APPEND:-} ]]; then printf '%s\n' "$FAKE_STATE_APPEND" >>"$st"; fi
 if [[ -n ${FAKE_STATE_SED:-} ]]; then sed -i "$FAKE_STATE_SED" "$st"; fi
-case " $* " in
+args=" $* "
+names=()
+while (($#)); do
+	case $1 in
+	-f) shift ;;
+	-*) ;;
+	*) names+=("$1") ;;
+	esac
+	shift
+done
+if ((${#names[@]})); then
+	rc=0
+	for n in "${names[@]}"; do
+		st=$(awk -F'\t' -v n="${n%:amd64}" '$2 == n { print $1; exit }' "$FAKE_DATA/apt/dpkg-status.tsv")
+		if [[ -z $st ]] || fake_purged "${n%:amd64}"; then
+			echo "dpkg-query: no packages found matching $n" >&2
+			rc=1
+			continue
+		fi
+		printf '%s' "$st"
+	done
+	exit "$rc"
+fi
+case $args in
 *' -W '*) cat "$FAKE_DATA/apt/dpkg-status.tsv" ;;
 *)
 	echo "fake dpkg-query: unhandled: $*" >&2