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/accountdelegate.cpp

@@ -0,0 +1,63 @@
+#include "accountdelegate.h"
+#include "memberlistmodel.h"
+#include <QPainter>
+#include <QFont>
+
+AccountDelegate::AccountDelegate(QObject *parent)
+    : QStyledItemDelegate(parent) {}
+
+void AccountDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
+                             const QModelIndex &index) const {
+    painter->save();
+
+    if (option.state & QStyle::State_Selected)
+        painter->fillRect(option.rect, option.palette.highlight());
+    else if (option.state & QStyle::State_MouseOver)
+        painter->fillRect(option.rect, option.palette.light());
+    else
+        painter->fillRect(option.rect, option.palette.alternateBase());
+
+    const int margin = 4;
+    const int iconSz = 24;
+
+    QIcon icon = qvariant_cast<QIcon>(index.data(Qt::DecorationRole));
+    if (!icon.isNull())
+        icon.paint(painter, option.rect.left() + margin, option.rect.top() + (option.rect.height() - iconSz) / 2, iconSz, iconSz);
+
+    const int x = option.rect.left() + iconSz + margin * 3;
+    const int w = option.rect.right() - x - margin;
+    const int yMid = option.rect.top() + option.rect.height() / 2;
+
+    QFont nameFont = painter->font();
+    nameFont.setBold(true);
+    nameFont.setPixelSize(13);
+    painter->setFont(nameFont);
+
+    QColor textColor = option.palette.color(QPalette::Text);
+    if (option.state & QStyle::State_Selected) textColor = option.palette.color(QPalette::HighlightedText);
+    if (index.data(Qt::UserRole + 2).toBool()) textColor = QColor("#4CAF50");
+    painter->setPen(textColor);
+
+    QString name = index.data(Qt::DisplayRole).toString();
+    painter->drawText(QRect(x, option.rect.top() + 2, w, yMid - option.rect.top() - 2),
+                      Qt::AlignLeft | Qt::AlignBottom, name);
+
+    QFont subFont = painter->font();
+    subFont.setBold(false);
+    subFont.setPixelSize(10);
+    painter->setFont(subFont);
+    painter->setPen(QColor(130, 130, 130));
+
+    QString sub = index.data(Qt::UserRole + 1).toString();
+    if (!sub.isEmpty())
+        painter->drawText(QRect(x, yMid + 2, w, option.rect.bottom() - yMid - 2),
+                          Qt::AlignLeft | Qt::AlignTop, sub);
+
+    painter->restore();
+}
+
+QSize AccountDelegate::sizeHint(const QStyleOptionViewItem &option,
+                                 const QModelIndex &index) const {
+    (void)option; (void)index;
+    return QSize(160, 36);
+}