Named-pipe transport for the DOSBox-X fork's namedpipe backend

Both devices now serve \.\pipe\vrio and \.\pipe\vplasma for the whole
app lifetime alongside the COM rows — the com0com-free path. Framing per
the pinned contract (0x00 len data / 0x01 DTR+RTS lines, one lines frame
on connect, unknown type = log + drop): PipeFraming/PipeFrameDecoder and
VRioPipeService (TX paced at the wire rate, peer DTR edges feed
HostHandshake) in VRio.Core, listener-only VPlasmaPipeService twin in
VPlasma.Core. Busy pipe names retry, so vRIO's built-in glass and the
standalone vPLASMA coexist. README documents the transport and the fork
conf lines.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/VRio.App/MainForm.cs

@@ -18,6 +18,9 @@ namespace VRio.App;
 /// RIOJoy at the other end of the null-modem pair, and every click here
 /// arrives at RIOJoy exactly as if the physical cockpit sent it; point the
 /// game's COM2 passthrough at the plasma pair and the glass lights up.
+/// Both devices also serve the DOSBox-X fork's named-pipe transport
+/// (<c>\\.\pipe\vrio</c>, <c>\\.\pipe\vplasma</c>) for the whole app
+/// lifetime — the com0com-free path.
 /// </summary>
 internal sealed class MainForm : Form
 {
@@ -36,8 +39,10 @@ internal sealed class MainForm : Form
 
     private readonly VRioDevice _device = new();
     private readonly VRioSerialService _service;
+    private readonly VRioPipeService _pipeService;
     private readonly VPlasmaDevice _plasmaDevice = new();
     private readonly VPlasmaSerialService _plasmaService;
+    private readonly VPlasmaPipeService _plasmaPipeService;
     private readonly PanelCanvas _canvas = new();
     private readonly PlasmaCanvas _plasmaCanvas = new(PanelCanvas.PlasmaDotPitch)
     {
@@ -190,6 +195,11 @@ internal sealed class MainForm : Form
 
         _service = new VRioSerialService(_device);
         _plasmaService = new VPlasmaSerialService(_plasmaDevice);
+        // The named-pipe endpoints for DOSBox-X's namedpipe serial backend.
+        // Unlike a COM port, a listening pipe costs nothing and conflicts with
+        // nothing, so both servers run for the whole app lifetime.
+        _pipeService = new VRioPipeService(_device);
+        _plasmaPipeService = new VPlasmaPipeService(_plasmaDevice);
         _router = new InputRouter(_device);
         _lampMirror = new KeyboardLampMirror(_device);
 
@@ -224,6 +234,17 @@ internal sealed class MainForm : Form
         _service.ConnectionChanged += open => RunOnUi(() => OnConnectionChanged(open));
         _service.HostHandshake += high => RunOnUi(() =>
             PrependLog(high ? "Host raised DTR (board-reset handshake)" : "Host dropped DTR"));
+        _pipeService.Logged += line => RunOnUi(() => PrependLog($"pipe: {line}"));
+        _pipeService.HostHandshake += high => RunOnUi(() =>
+            PrependLog(high ? "Pipe host raised DTR (board-reset handshake)" : "Pipe host dropped DTR"));
+        _pipeService.ClientChanged += connected => RunOnUi(() =>
+        {
+            // The RIO is a single-host device; two live transports means two
+            // hosts fighting over one board.
+            if (connected && _service.IsOpen)
+                PrependLog($"Warning: a pipe client connected while {_service.PortName} is open — close one transport.");
+        });
+        _plasmaPipeService.Logged += line => RunOnUi(() => PrependLog($"vPLASMA pipe: {line}"));
 
         // Built-in plasma glass: a pure listener on its own port, same gestures
         // as the standalone vPLASMA — double-click cycles the self-test pages,
@@ -305,6 +326,8 @@ internal sealed class MainForm : Form
             _rawKeyboard.Dispose();
             _service.Dispose();
             _plasmaService.Dispose();
+            _pipeService.Dispose();
+            _plasmaPipeService.Dispose();
         };
 
         RefreshPorts();
@@ -313,6 +336,8 @@ internal sealed class MainForm : Form
         LoadBindings();
         _plasmaCanvas.UpdateFrom(_plasmaDevice); // paint the power-on frame
         AutoOpenPreferredPorts();
+        _pipeService.Start();
+        _plasmaPipeService.Start();
     }
 
     private Panel BuildControlStrip()