[idd] ipc: connect LGInput to LGIdd

Move the reusable named-pipe endpoint and shared support code into
the LGCommon static library.

Run a dedicated server in LGIdd and a reconnecting client in
LGInput, with device-lifecycle handling and report framing.

Refactor the helper pipe to use the same endpoint implementation.

idd/LGIdd/ipc/CInputPipeServer.cpp

@@ -0,0 +1,75 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include "ipc/CInputPipeServer.h"
+
+#include "CDebug.h"
+#include "InputPipeProtocol.h"
+
+#include <string.h>
+
+CInputPipeServer g_inputPipeServer;
+
+bool CInputPipeServer::Init()
+{
+  AcquireSRWLockExclusive(&m_sendLock);
+  m_sequence = 0;
+  ReleaseSRWLockExclusive(&m_sendLock);
+
+  m_endpoint.SetHandler(this);
+  return m_endpoint.Start(
+    LG_INPUT_PIPE_NAME,
+    CPipeEndpoint::Mode::Server,
+    sizeof(LGInputPipeMessage));
+}
+
+void CInputPipeServer::DeInit()
+{
+  m_endpoint.Stop();
+}
+
+bool CInputPipeServer::SendReport(const void * report, size_t size)
+{
+  if (!report || !size || size > LG_INPUT_PIPE_MAX_REPORT_SIZE)
+    return false;
+
+  LGInputPipeMessage message = {};
+  message.magic = LG_INPUT_PIPE_MAGIC;
+  message.version = LG_INPUT_PIPE_VERSION;
+  message.type = LG_INPUT_PIPE_MESSAGE_REPORT;
+  message.payloadSize = static_cast<uint32_t>(size);
+  memcpy(message.payload, report, size);
+
+  AcquireSRWLockExclusive(&m_sendLock);
+  message.sequence = ++m_sequence;
+  const bool sent = m_endpoint.Send(&message, sizeof(message));
+  ReleaseSRWLockExclusive(&m_sendLock);
+  return sent;
+}
+
+bool CInputPipeServer::OnPipeMessage(
+  const void * message,
+  size_t size)
+{
+  UNREFERENCED_PARAMETER(message);
+  UNREFERENCED_PARAMETER(size);
+  DEBUG_WARN("LGInput sent an unexpected message");
+  return false;
+}