- u_async.c: process immediate_queue BEFORE epoll_wait in uasync_poll
- stcp_link.c: defensive NULL etcp_conn/etcp_link in stcp_link_close
- utun_instance.c: move stcp_server_list_destroy_all to Phase J (before ETCP),
add deferred drain in both Phase J and L
- stcp.h/c: STCP_HS_ENC_CLIENT 6→38, STCP_HS_ENC_SERVER 7→39,
exchange ed25519_pubkey in both handshake directions
- etcp_connections.c: copy peer_ed25519 from STCP to ETCP_CONN in
etcp_link_enter_ready_tcp; guard link->etcp in tcp_link_close_cb
- chat_sync.c: fix lk->conn NULL dereference for TCP links
- test_stcp.c: update stcp_server_create/stcp_client_connect callsites
- tools/chat_tcp_test: change transport udp→tcp
- find_third_node: use nd->inst->connections instead of group->senders_list
- on_conn_up callback auto-calls trigger_checks (no BGP handshake needed)
- Remove group param from link_ready, request_check_all — nat_detection self-sufficient
- Remove trigger_checks + route_ping_cancel_for_conn from public API (internal only)
- topo_group.c: removed last nat_detection_trigger_checks call — completely decoupled
- Header: 4-line summary, no duplicate function list, 7 public functions
- Assign ETCP_ID_NAT_DETECTION = 0x02, etcp_bind in create, etcp_unbind in destroy
- nat_detection_receive_cbk: own packet dispatcher (PING_REQ/RESP, NAT_INFO/CHECK_REQ)
- 4 handle_* become static internal, send_nat_check_req stays static (dead code)
- Rename TOPO_* -> NATDET_*: all subcommands, structs, message types
- Remove all NAT/PING constants and structs from topo_group.h
- Remove dispatch lines and subcmd_name cases from topo_group_receive_cbk
- API: clear sections (lifecycle/internal service/control/test helpers)
- trigger_checks: marked with IMPORTANT note about call order (must be after add_to_senders)