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/09-tunnel.sh

@@ -0,0 +1,40 @@
+# Port forwards: named, ad hoc, --forward with a shell, port in use.
+config <<'EOF'
+resolver:
+  strategies: [management_subnet, primary_ip]
+  management_subnets: [10.231.1.0/24]
+ssh:
+  default_user: ops
+  forwards:
+    web: {local: "18081:127.0.0.1:8081"}
+  rules:
+    - match: {kind: vm, instance: fsn}
+      proxy_jump: ops@10.231.0.30
+EOF
+tunnel_test() { # NAME PORT WANT ARGS...
+  local name=$1 port=$2 want=$3 pid out
+  shift 3
+  "$@" >"$HOME/tunnel.log" 2>&1 &
+  pid=$!
+  if wait_for 15 curl -sf "http://127.0.0.1:$port/"; then
+    out=$(curl -s "http://127.0.0.1:$port/")
+    [[ $out == *"$want"* ]] && ok "$name" || bad "$name" "curl: $out"
+  else
+    bad "$name" "tunnel did not open: $(cat "$HOME/tunnel.log")"
+  fi
+  kill "$pid" 2>/dev/null
+  wait "$pid" 2>/dev/null
+}
+tunnel_test "named forward" 18081 "hello from fsn1-pve1" netssh tunnel fsn/fsn1-pve1.hoster.test web
+expect_out "tunnel notice" "forwarding -L 18081:127.0.0.1:8081 via fsn1-pve1.hoster.test" cat "$HOME/tunnel.log"
+tunnel_test "ad hoc spec through the bastion" 18082 "hello from web1" netssh tunnel fsn/web1 18082:127.0.0.1:8081
+tunnel_test "--forward with a remote command" 18081 "hello from fsn1-pve2" netssh --forward web fsn/fsn1-pve2.hoster.test sleep 30
+
+netssh tunnel fsn/fsn1-pve1.hoster.test web >/dev/null 2>&1 &
+holder=$!
+wait_for 15 curl -sf http://127.0.0.1:18081/
+expect_fail "port in use fails instead of hanging" "Address in use" timeout 20 netssh tunnel fsn/fsn1-pve2.hoster.test web
+kill "$holder"; wait "$holder" 2>/dev/null
+
+expect_fail "unknown forward lists the configured ones" "available: web" netssh tunnel fsn/fsn1-pve1.hoster.test db
+expect_fail "tunnel without forward" "forwards for fsn/fsn1-pve1.hoster.test: web" netssh tunnel fsn/fsn1-pve1.hoster.test