vRIO: virtual RIO cockpit device emulator

Speaks the device side of the RIO serial protocol (per riojoy's
PROTOCOL.md) on a COM port, behind an interactive replica of the
profile editor's cockpit panel: click cells to press buttons/keys,
drag the encoder gauges to move the five analog axes, and watch
host-commanded lamp states (incl. flash modes) light the cells.

Device behavior grounded in the real v4.2 firmware dump: version 4.2,
4-retry NAK budget ending in RESTART, and an optional emulation of the
analog reply-wedge latch leak for exercising host recovery watchdogs.

Verified: 33 unit tests, plus an interop harness driving RIOJoy's
actual RioSerialLink against VRioDevice over an in-memory transport
(version/check/analog/lamp/button/keypad/reset all round-trip).

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

src/VRio.App/VRio.App.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net48</TargetFramework>
+    <Nullable>enable</Nullable>
+    <UseWindowsForms>true</UseWindowsForms>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <LangVersion>latest</LangVersion>
+    <ApplicationManifest>app.manifest</ApplicationManifest>
+    <AssemblyTitle>vRIO — Virtual RIO device</AssemblyTitle>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\VRio.Core\VRio.Core.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="PolySharp" Version="1.14.1">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+</Project>