stcp: ed25519 pubkey exchange in handshake, fix instance destroy segfault, fix chat_tcp_test

- 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

tools/chatgui-android/app/src/main/cpp/CMakeLists.txt

@@ -0,0 +1,60 @@
+cmake_minimum_required(VERSION 3.22)
+project("utun_bridge")
+
+set(LIB_DIR  ${CMAKE_CURRENT_SOURCE_DIR}/../../../../../../lib)
+set(SRC_DIR  ${CMAKE_CURRENT_SOURCE_DIR}/../../../../../../src)
+set(CFG_DIR  ${CMAKE_CURRENT_SOURCE_DIR}/../../../../libutun_lite)
+set(JNI_DIR  ${CMAKE_CURRENT_SOURCE_DIR}/../../../../jni_bridge)
+set(TOOLS_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../../../../../..)
+
+include(${CFG_DIR}/utun_sources.cmake)
+utun_setup_sources("${LIB_DIR}" "${SRC_DIR}" "${CFG_DIR}" "${TOOLS_DIR}")
+
+# Include Opus codec wrapper (was excluded before voice support)
+# list(FILTER UTUN_SOURCES EXCLUDE REGEX "opus_codec\\.c$")
+
+# Exclude tun_windows and tun_freebsd (Android is Linux-like)
+list(FILTER UTUN_SOURCES EXCLUDE REGEX "tun_windows\\.c$")
+list(FILTER UTUN_SOURCES EXCLUDE REGEX "tun_freebsd\\.c$")
+
+# Add libopus sources (for voice recording)
+file(GLOB_RECURSE _OPUS_SRC "${LIB_DIR}/libopus/src/*.c"
+     "${LIB_DIR}/libopus/celt/*.c" "${LIB_DIR}/libopus/silk/*.c"
+     "${LIB_DIR}/libopus/silk/float/*.c")
+list(FILTER _OPUS_SRC EXCLUDE REGEX "/x86/")
+list(APPEND UTUN_SOURCES ${_OPUS_SRC})
+list(APPEND UTUN_INCLUDE_DIRS "${LIB_DIR}/libopus" "${LIB_DIR}/libopus/include"
+     "${LIB_DIR}/libopus/celt" "${LIB_DIR}/libopus/silk" "${LIB_DIR}/libopus/silk/float")
+# Opus requires these to be defined (or HAVE_CONFIG_H + config.h with VAR_ARRAYS)
+list(APPEND UTUN_DEFINES OPUS_BUILD VAR_ARRAYS USE_ALLOCA)
+
+# Prebuilt OpenSSL (cross-compiled for Android)
+set(OPENSSL_DIR ${CMAKE_CURRENT_SOURCE_DIR}/openssl/${ANDROID_ABI})
+add_library(openssl_crypto STATIC IMPORTED)
+set_target_properties(openssl_crypto PROPERTIES
+    IMPORTED_LOCATION "${OPENSSL_DIR}/lib/libcrypto.a"
+)
+
+# OBJECT library: compile .c once, link into SHARED
+add_library(utun_core OBJECT ${UTUN_SOURCES})
+target_include_directories(utun_core PRIVATE
+    ${UTUN_INCLUDE_DIRS} ${JNI_DIR} ${OPENSSL_DIR}/include
+)
+target_compile_definitions(utun_core PRIVATE ${UTUN_DEFINES} __ANDROID__)
+set_target_properties(utun_core PROPERTIES C_STANDARD 99 C_STANDARD_REQUIRED ON)
+
+# JNI bridge + link into shared library
+add_library(utun SHARED
+    ${JNI_DIR}/android_jni_bridge.c
+    ${JNI_DIR}/android_udp_log.c
+    $<TARGET_OBJECTS:utun_core>
+)
+
+target_include_directories(utun PRIVATE
+    ${UTUN_INCLUDE_DIRS} ${JNI_DIR} ${OPENSSL_DIR}/include
+)
+target_compile_definitions(utun PRIVATE ${UTUN_DEFINES} __ANDROID__)
+set_target_properties(utun PROPERTIES C_STANDARD 99 C_STANDARD_REQUIRED ON)
+
+find_library(log-lib log)
+target_link_libraries(utun ${log-lib} openssl_crypto)