crates/ctl/src/commands/responder.rs (~9KB, 13.21% coverage, 14/106 lines; ~71 lines to hit 80%). Responder backend selection + listing.

Suggested tests

• Backend resolution from agent.toml (ufw / iptables / nftables / pf / xdp / default)
• List commands output for each backend
• Missing [responder] section -> default
• Invalid backend name -> clear error

Acceptance

cargo test -p innerwarden-ctl responder >= 5 new tests; file coverage >= 80%.
Estimated effort: ~3h.