chat: invite-ссылки с выбором достижимого узла + tcp_io фикс half-close FIN

- Общий модуль invite_build: сборка utun://-ссылок, авто-выбор лучшего
  достижимого узла, список кандидатов (вынесено из android jni_bridge)
- chatgui: диалог invite с выбором узла (комбобокс), события INVITE_CANDIDATES /
  INVITE_LINK_READY через gui_bridge
- headless/chatcli: invite <ch_id> [node_id], команда invite_nodes
- tcp_io: error_cb отличает грациозный EPOLLHUP (SO_ERROR==0) от реальной ошибки —
  при приостановленном чтении FIN не роняет недослейные данные (фикс flaky half-close)
- run_test.sh: half-close echo на выделенном порту 19190 + отдельный DNAT (был недостижим)

tools/chatgui/src/sound_manager.cpp

@@ -32,10 +32,19 @@ bool SoundManager::init() {
     return true;
 }
 
+void SoundManager::clearCurrentPcm() {
+    if (m_currentPcmSound) { ma_sound_uninit(m_currentPcmSound); delete m_currentPcmSound; m_currentPcmSound = nullptr; }
+    if (m_currentPcmBuffer) {
+        ma_audio_buffer* buf = (ma_audio_buffer*)m_currentPcmBuffer;
+        ma_audio_buffer_uninit(buf); delete buf; m_currentPcmBuffer = nullptr;
+    }
+    m_currentPcmSampleRate = 0;
+}
+
 void SoundManager::shutdown() {
     if (!m_initialized) return;
 
-    stopCurrentPcm();
+    clearCurrentPcm();
 
     for (auto it = m_sounds.begin(); it != m_sounds.end(); ++it) {
         if (it->sound) { ma_sound_uninit(it->sound); delete it->sound; }
@@ -45,11 +54,6 @@ void SoundManager::shutdown() {
 
     DEBUG_DEBUG(DEBUG_CATEGORY_GENERAL, "SoundManager: before ma_engine_uninit engine=%p", (void*)m_engine);
     if (m_engine) { ma_engine_uninit(m_engine); delete m_engine; m_engine = nullptr; }
-    if (m_currentPcmSound) { delete m_currentPcmSound; m_currentPcmSound = nullptr; }
-    if (m_currentPcmBuffer) {
-        ma_audio_buffer* buf = (ma_audio_buffer*)m_currentPcmBuffer;
-        ma_audio_buffer_uninit(buf); delete buf; m_currentPcmBuffer = nullptr;
-    }
     DEBUG_DEBUG(DEBUG_CATEGORY_GENERAL, "SoundManager: after ma_engine_uninit");
     m_initialized = false;
 }
@@ -152,7 +156,7 @@ void SoundManager::playRawPcm(const int16_t* pcm, int sampleCount, int sampleRat
         DEBUG_WARN(DEBUG_CATEGORY_DEBUG, "SoundManager::playRawPcm: not initialized");
         return;
     }
-    if (m_currentPcmSound) ma_sound_stop(m_currentPcmSound);
+    clearCurrentPcm();
     m_currentPcmSampleRate = sampleRate;
     DEBUG_DEBUG(DEBUG_CATEGORY_DEBUG, "SoundManager::playRawPcm: %d samples %dHz %dch", sampleCount, sampleRate, channels);
 
@@ -189,8 +193,7 @@ void SoundManager::resumeCurrentPcm() {
 }
 
 void SoundManager::stopCurrentPcm() {
-    if (m_currentPcmSound) ma_sound_stop(m_currentPcmSound);
-    m_currentPcmSampleRate = 0;
+    clearCurrentPcm();
 }
 
 unsigned long long SoundManager::currentPcmCursor() const {