test: add a local Docker test environment for all features

testenv/ starts two real NetBox 4.7 instances (v2 and v1 token), SSH
targets on public, mgmt, and prod networks, a jump host, an IPv6-only
host, a static host, and a client with ssh, sftp, scp, tmux, zellij,
bash, zsh, and fish. A seed script fills NetBox through the REST API.

141 end-to-end checks cover cache and refresh filters, connecting,
all resolver strategies, multiple instances, shortcuts and rewrites,
SSH options and rules, static hosts, sftp/scp incl. IPv6 and jump
hosts, tunnels, local notes and NetBox comments, completion and shell
hooks, the TUI (driven through tmux), the configurator, and uninstall.

Local only: testenv/up.sh, test.sh, shell.sh, down.sh. Not part of
CI/CD.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

testenv/tests/lib.sh

@@ -0,0 +1,78 @@
+# Helpers for the netssh test environment. Sourced by run.sh, the tests, and
+# shell.sh inside the client container.
+
+# shellcheck disable=SC1091
+. /state/env
+RESULTS=${RESULTS:-/tmp/netssh-results}
+
+# new_home gives each test file its own netssh config, cache, notes, and rc files.
+new_home() {
+  HOME=$(mktemp -d /tmp/home.XXXXXX)
+  export HOME XDG_CONFIG_HOME="$HOME/.config" XDG_CACHE_HOME="$HOME/.cache" SHELL=/bin/bash
+  mkdir -p "$XDG_CONFIG_HOME" "$XDG_CACHE_HOME"
+  unset TMUX ZELLIJ NETSSH_NETBOX_URL NETSSH_NETBOX_TOKEN
+  cd "$HOME" || exit 1
+}
+
+# base_config prints both NetBox instances followed by stdin.
+base_config() { cat /state/netssh.yaml -; }
+
+# config writes the netssh config: both NetBox instances plus stdin.
+config() { base_config >"$XDG_CONFIG_HOME/netssh.yaml"; }
+
+# config_only writes stdin as the whole config (no NetBox).
+config_only() { cat >"$XDG_CONFIG_HOME/netssh.yaml"; }
+
+ok() {
+  echo "ok $CURRENT: $1" >>"$RESULTS"
+  printf '  \033[32mok\033[0m    %s\n' "$1"
+}
+bad() {
+  echo "FAIL $CURRENT: $1" >>"$RESULTS"
+  printf '  \033[31mFAIL\033[0m  %s\n' "$1"
+  printf '%s\n' "$2" | sed 's/^/        /'
+}
+
+# check NAME CMD... — CMD must succeed.
+check() {
+  local name=$1 out
+  shift
+  if out=$("$@" 2>&1); then ok "$name"; else bad "$name" "exit $?: $out"; fi
+}
+
+# expect_out NAME WANT CMD... — CMD must succeed and print WANT (substring).
+expect_out() {
+  local name=$1 want=$2 out rc
+  shift 2
+  out=$("$@" 2>&1) && rc=0 || rc=$?
+  if [ "$rc" = 0 ] && [[ $out == *"$want"* ]]; then ok "$name"; else bad "$name" "want: $want
+got (exit $rc): $out"; fi
+}
+
+# expect_eq NAME WANT CMD... — CMD must succeed and print exactly WANT.
+expect_eq() {
+  local name=$1 want=$2 out rc
+  shift 2
+  out=$("$@" 2>&1) && rc=0 || rc=$?
+  if [ "$rc" = 0 ] && [ "$out" = "$want" ]; then ok "$name"; else bad "$name" "want: $want
+got (exit $rc): $out"; fi
+}
+
+# expect_fail NAME WANT CMD... — CMD must fail and print WANT (substring).
+expect_fail() {
+  local name=$1 want=$2 out rc
+  shift 2
+  out=$("$@" 2>&1) && rc=0 || rc=$?
+  if [ "$rc" != 0 ] && [[ $out == *"$want"* ]]; then ok "$name"; else bad "$name" "want failure with: $want
+got (exit $rc): $out"; fi
+}
+
+# wait_for TIMEOUT CMD... — retry CMD every 0.2 s until it succeeds.
+wait_for() {
+  local deadline=$((SECONDS + $1))
+  shift
+  until "$@" >/dev/null 2>&1; do
+    [ $SECONDS -ge $deadline ] && return 1
+    sleep 0.2
+  done
+}