Pipe endpoints join the connection pickers; no more COM11/COM12 auto-bind

Each device row now serves one endpoint at a time, picked from a list of
pipe:vrio / pipe:vplasma (first, default) plus the machine's COM ports —
nothing opens automatically at startup. The pipe services gained an
IsListening property and are started/stopped by the row's Open/Close
button instead of running for the whole app lifetime, which also retires
the dual-transport warning. Status line shows the active endpoint;
OFFLINE when none. Standalone vPLASMA is unchanged (hardwired COM12 +
permanent pipe). Also fixes the xUnit1031 warnings in the plasma pipe
tests.

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

tests/VPlasma.Core.Tests/VPlasmaPipeServiceTests.cs

@@ -66,7 +66,7 @@ public class VPlasmaPipeServiceTests
     }
 
     [Fact]
-    public void Unknown_frame_type_drops_the_client_and_server_recovers()
+    public async Task Unknown_frame_type_drops_the_client_and_server_recovers()
     {
         string name = UniqueName();
         var device = new VPlasmaDevice();
@@ -85,8 +85,9 @@ public class VPlasmaPipeServiceTests
                 try { return bad.Read(new byte[1], 0, 1) == 0; }
                 catch (IOException) { return true; }
             });
-            Assert.True(eof.Wait(2000), "server did not drop the connection");
-            Assert.True(eof.Result);
+            Assert.True(await Task.WhenAny(eof, Task.Delay(2000)) == eof,
+                "server did not drop the connection");
+            Assert.True(await eof);
         }
 
         using var good = Connect(name);