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/13-configure.sh

@@ -0,0 +1,9 @@
+# The configurator in huh's accessible mode: without NetBox, add a static host,
+# save, then connect. Menu numbers follow the order in internal/setup.
+config_only </dev/null
+rm -f "$XDG_CONFIG_HOME/netssh.yaml"
+#                          no NetBox, static hosts, add, name, address, user, port, tags, back, save
+out=$(python3 /tests/drive.py 2 4 1 legacy-box 10.231.0.50 admin "" legacy 5 8)
+[[ $out == *"Config saved"* ]] && ok "configure saves" || bad "configure saves" "$out"
+expect_out "config has the host" 'address: "10.231.0.50"' cat "$XDG_CONFIG_HOME/netssh.yaml"
+expect_eq "connect to the configured host" "admin" netssh legacy-box whoami