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/src/main.cpp

@@ -0,0 +1,133 @@
+#include <QApplication>
+#include <QPalette>
+#include <QStyleFactory>
+#include <QDir>
+#include <cstdio>
+#ifdef _WIN32
+#include <windows.h>
+#include <tlhelp32.h>
+#endif
+#include "mainwindow.h"
+#include "../db/db_manager.h"
+#include "../transport/node_config.h"
+#include "../transport/utun_node.h"
+#include "../../lib/debug_config.h"
+
+#ifdef _WIN32
+static UtunNode* g_ctrl_node = nullptr;
+
+static DWORD count_threads(void) {
+    DWORD pid = GetCurrentProcessId(), count = 0;
+    HANDLE snap = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);
+    if (snap == INVALID_HANDLE_VALUE) return 0;
+    THREADENTRY32 te = { sizeof(te) };
+    if (Thread32First(snap, &te)) {
+        do { if (te.th32OwnerProcessID == pid) count++; }
+        while (Thread32Next(snap, &te));
+    }
+    CloseHandle(snap);
+    return count;
+}
+
+static BOOL WINAPI console_ctrl_handler(DWORD dwCtrlType) {
+    if (dwCtrlType == CTRL_C_EVENT || dwCtrlType == CTRL_BREAK_EVENT) {
+        if (g_ctrl_node) g_ctrl_node->requestStop();
+        return TRUE;
+    }
+    return FALSE;
+}
+#endif
+
+static struct ShutdownSentinel {
+    ~ShutdownSentinel() {
+        DEBUG_INFO(DEBUG_CATEGORY_GENERAL, "main: static destructors done");
+#ifdef _WIN32
+        DWORD threads = count_threads();
+        DEBUG_INFO(DEBUG_CATEGORY_GENERAL, "main: threads at exit=%lu", (unsigned long)threads);
+        if (threads > 4) {
+            DEBUG_WARN(DEBUG_CATEGORY_GENERAL, "main: %lu hanging threads, TerminateProcess", (unsigned long)threads);
+            fflush(nullptr);
+            TerminateProcess(GetCurrentProcess(), 0);
+        }
+#endif
+    }
+} g_shutdown_sentinel;
+
+int main(int argc, char *argv[]) {
+    QApplication app(argc, argv);
+    app.setApplicationName("Chat");
+    app.setQuitOnLastWindowClosed(false);
+
+    app.setStyle(QStyleFactory::create("Fusion"));
+    QPalette p;
+    p.setColor(QPalette::Window,          QColor(53, 53, 53));
+    p.setColor(QPalette::WindowText,      QColor(220, 220, 220));
+    p.setColor(QPalette::Base,            QColor(42, 42, 42));
+    p.setColor(QPalette::AlternateBase,   QColor(66, 66, 66));
+    p.setColor(QPalette::ToolTipBase,     QColor(25, 25, 25));
+    p.setColor(QPalette::ToolTipText,     QColor(220, 220, 220));
+    p.setColor(QPalette::Text,            QColor(220, 220, 220));
+    p.setColor(QPalette::Button,          QColor(53, 53, 53));
+    p.setColor(QPalette::ButtonText,      QColor(220, 220, 220));
+    p.setColor(QPalette::BrightText,      Qt::red);
+    p.setColor(QPalette::Link,            QColor(42, 130, 218));
+    p.setColor(QPalette::Highlight,       QColor(42, 130, 218));
+    p.setColor(QPalette::HighlightedText, Qt::white);
+    p.setColor(QPalette::Disabled, QPalette::Text, QColor(127, 127, 127));
+    p.setColor(QPalette::Disabled, QPalette::ButtonText, QColor(127, 127, 127));
+    app.setPalette(p);
+
+    QString cfgPath = QCoreApplication::applicationDirPath() + "/chatgui.cfg";
+
+    NodeConfig cfg(cfgPath);
+    bool needSave = false;
+
+    if (!cfg.exists()) {
+        if (!cfg.create("chatgui", 1333)) {
+            qCritical("Failed to create config: %s", qPrintable(cfgPath));
+            return 1;
+        }
+    } else {
+        if (!cfg.load()) {
+            qCritical("Cannot open/read config file: %s", qPrintable(cfgPath));
+            return 1;
+        }
+        if (cfg.hasErrors()) {
+            for (const auto& err : cfg.errors())
+                fprintf(stderr, "CONFIG ERROR: %s\n", qPrintable(err));
+            return 1;
+        }
+        if (cfg.privKey().length() != 64 || cfg.pubKey().length() != 64) {
+            qWarning("Config: keys missing/invalid, regenerating identity");
+            cfg.generateIdentity();
+            needSave = true;
+        }
+        if (cfg.nodeId().length() != 16) {
+            qWarning("Config: my_node_id missing/invalid, regenerating identity");
+            cfg.generateIdentity();
+            needSave = true;
+        }
+        if (needSave)
+            cfg.save();
+    }
+
+    QString dbPath = cfg.dbPath();
+    if (dbPath.isEmpty()) dbPath = "chat_data";
+    if (!QDir::isAbsolutePath(dbPath))
+        dbPath = QCoreApplication::applicationDirPath() + "/" + dbPath;
+    QDir(dbPath).mkpath(".");
+
+    DbManager db;
+    MainWindow w(nullptr, &db, cfgPath, dbPath, cfg.debugFile(),
+                 cfg.debugLevel(), cfg.debugCategories());
+    w.show();
+
+#ifdef _WIN32
+    g_ctrl_node = w.utunNode();
+    SetConsoleCtrlHandler(console_ctrl_handler, TRUE);
+#endif
+
+    int ret = app.exec();
+    DEBUG_INFO(DEBUG_CATEGORY_GENERAL, "main: app.exec() returned %d", ret);
+    return ret;
+}