- 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
- audio_compressor.h/c moved to lib/ (alongside opus_codec, mem, debug_config)
- lib/Makefile.am: added to libuasync_a_SOURCES
- utun_sources.cmake: removed from _cfg_src (GLOB from lib/ picks it up)
- tests/Makefile.am: test_audio_compressor added to check_PROGRAMS
- test includes simplified (debug_config.h, mem.h — lib/ in include path)