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/VPlasma.App/MainForm.cs

@@ -7,6 +7,9 @@ namespace VPlasma.App;
 /// device end is hardwired to <see cref="PortName"/> (the plasma side of the
 /// second com0com pair) and opened automatically — a retry timer keeps
 /// trying while the port is missing or busy, and reopens it if it dies. The
+/// DOSBox-X fork's named-pipe transport (<c>\\.\pipe\vplasma</c>) is served
+/// permanently alongside it (if vRIO's built-in glass already holds the
+/// pipe name, the server just retries until it frees up). The
 /// title bar carries the port status; double-clicking the glass cycles the
 /// self-test pages (banner, charset, graphics) through the wire parser, and
 /// a right-click resets the display to its power-on state.
@@ -18,6 +21,7 @@ internal sealed class MainForm : Form
 
     private readonly VPlasmaDevice _device = new();
     private readonly VPlasmaSerialService _service;
+    private readonly VPlasmaPipeService _pipeService;
     private readonly PlasmaCanvas _canvas = new();
 
     private readonly System.Windows.Forms.Timer _reconnectTimer = new() { Interval = 3000 };
@@ -32,6 +36,7 @@ internal sealed class MainForm : Form
         StartPosition = FormStartPosition.CenterScreen;
 
         _service = new VPlasmaSerialService(_device);
+        _pipeService = new VPlasmaPipeService(_device);
 
         _canvas.Location = new Point(0, 0);
         Controls.Add(_canvas);
@@ -39,6 +44,7 @@ internal sealed class MainForm : Form
         // Device / service events arrive on the serial reader thread; marshal to the UI.
         _device.Updated += () => RunOnUi(() => _canvas.UpdateFrom(_device));
         _service.ConnectionChanged += _ => RunOnUi(UpdateTitle);
+        _pipeService.ClientChanged += _ => RunOnUi(UpdateTitle);
 
         _canvas.DoubleClick += (_, _) => RunSelfTest();
         _canvas.MouseClick += (_, e) =>
@@ -55,10 +61,12 @@ internal sealed class MainForm : Form
         {
             _reconnectTimer.Dispose();
             _service.Dispose();
+            _pipeService.Dispose();
         };
 
         _canvas.UpdateFrom(_device);
         EnsureOpen();
+        _pipeService.Start();
     }
 
     private void EnsureOpen()
@@ -82,6 +90,8 @@ internal sealed class MainForm : Form
         string status = _service.IsOpen
             ? $"{PortName} @ 9600 8N1"
             : $"{PortName} unavailable — retrying";
+        if (_pipeService.IsClientConnected)
+            status += "  •  pipe host connected";
         Text = $"vPLASMA v{Application.ProductVersion} — {status}";
     }