fix(win): stop TLS sockets busy-spinning the socket poll loop

pollSocket() caches a socket's writability and skips waiting once it's
known writable, relying on writeSocket() to clear the cache on
WSAEWOULDBLOCK. SecureSocket writes via SSL_write(), bypassing
writeSocket() entirely, so the cache never clears and the multiplexer
spins at a zero timeout instead of blocking whenever TLS hits
backpressure.

Add IArchNetwork::resetPollWriteOnSocket() and call it from
checkResult()'s SSL_ERROR_WANT_WRITE case, mirroring writeSocket()'s
existing WSAEWOULDBLOCK handling.

src/lib/arch/IArchNetwork.h

@@ -211,6 +211,16 @@ public:
   */
   virtual size_t writeSocket(ArchSocket s, const void *buf, size_t len) = 0;
 
+  //! Reset the writable poll hint for a socket
+  /*!
+  Tells pollSocket() to wait for a fresh writable notification instead of
+  assuming the socket is still writable. Needed by callers that write to a
+  socket without going through writeSocket(), e.g. OpenSSL's SSL_write().
+  */
+  virtual void resetPollWriteOnSocket(ArchSocket)
+  {
+  }
+
   //! Check error on socket
   /*!
   If the socket \c s is in an error state then throws an appropriate

src/lib/arch/win32/ArchNetworkWinsock.cpp

@@ -1,5 +1,6 @@
 /*
  * Deskflow -- mouse and keyboard sharing utility
+ * SPDX-FileCopyrightText: (C) 2026 Deskflow Developers
  * SPDX-FileCopyrightText: (C) 2012 - 2016 Synergy App Ltd
  * SPDX-FileCopyrightText: (C) 2002 Chris Schoeneman
  * SPDX-License-Identifier: GPL-2.0-only WITH LicenseRef-OpenSSL-Exception
@@ -557,6 +558,12 @@ size_t ArchNetworkWinsock::writeSocket(ArchSocket s, const void *buf, size_t len
   return static_cast<size_t>(n);
 }
 
+void ArchNetworkWinsock::resetPollWriteOnSocket(ArchSocket s)
+{
+  assert(s != nullptr);
+  s->m_pollWrite = true;
+}
+
 void ArchNetworkWinsock::throwErrorOnSocket(ArchSocket s)
 {
   assert(s != nullptr);

src/lib/arch/win32/ArchNetworkWinsock.h

@@ -1,5 +1,6 @@
 /*
  * Deskflow -- mouse and keyboard sharing utility
+ * SPDX-FileCopyrightText: (C) 2026 Deskflow Developers
  * SPDX-FileCopyrightText: (C) 2012 - 2016 Synergy App Ltd
  * SPDX-FileCopyrightText: (C) 2002 Chris Schoeneman
  * SPDX-License-Identifier: GPL-2.0-only WITH LicenseRef-OpenSSL-Exception
@@ -71,6 +72,7 @@ public:
   void unblockPollSocket(ArchThread thread) override;
   size_t readSocket(ArchSocket s, void *buf, size_t len) override;
   size_t writeSocket(ArchSocket s, const void *buf, size_t len) override;
+  void resetPollWriteOnSocket(ArchSocket s) override;
   void throwErrorOnSocket(ArchSocket) override;
   bool setNoDelayOnSocket(ArchSocket, bool noDelay) override;
   void setKeepAliveOnSocket(ArchSocket, bool keepAlive) override;

src/lib/net/SecureSocket.cpp

@@ -556,8 +556,8 @@ void SecureSocket::checkResult(int status, int &retry)
     break;
 
   case SSL_ERROR_WANT_WRITE:
-    // Need to make sure the socket is known to be writable so the impending
-    // poll action actually triggers on a write.
+    // SSL_write() bypasses writeSocket(), so reset the poll hint ourselves.
+    ARCH->resetPollWriteOnSocket(getSocket());
     setWritable(true);
     retry++;
     LOG_VERBOSE("want to write, error=%d, attempt=%d", errorCode, retry);