[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/LGInput/ipc/CInputPipeClient.h

@@ -0,0 +1,44 @@
+/**
+ * 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
+ */
+
+#pragma once
+
+#include "CPipeEndpoint.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+class CInputPipeClient : private IPipeEndpointHandler
+{
+public:
+  ~CInputPipeClient() { Stop(); }
+
+  bool Start();
+  void Stop();
+  bool IsConnected() const { return m_endpoint.IsConnected(); }
+
+private:
+  void OnPipeConnected() override;
+  void OnPipeDisconnected() override;
+  bool OnPipeMessage(const void * message, size_t size) override;
+
+  CPipeEndpoint m_endpoint;
+  uint64_t m_lastSequence = 0;
+};