feat(interop): add NdiRuntimeProbe with version-mismatch result

src/TeamsISO.Engine/Interop/NdiRuntimeProbe.cs

@@ -0,0 +1,35 @@
+namespace TeamsISO.Engine.Interop;
+
+/// <summary>
+/// Result of an NDI runtime version check.
+/// </summary>
+public abstract record NdiRuntimeProbeResult
+{
+    public sealed record Match(string Version) : NdiRuntimeProbeResult;
+    public sealed record Mismatch(string Detected, string Expected) : NdiRuntimeProbeResult;
+}
+
+/// <summary>
+/// Compares the installed NDI runtime version (read via <see cref="INdiInterop.GetRuntimeVersion"/>)
+/// against the version expected by the bundled SDK headers. Surfaces mismatches so the engine
+/// can raise <c>EngineAlert.NdiRuntimeMismatch</c>.
+/// </summary>
+public sealed class NdiRuntimeProbe
+{
+    private readonly INdiInterop _interop;
+    private readonly string _expectedVersion;
+
+    public NdiRuntimeProbe(INdiInterop interop, string expectedVersion)
+    {
+        _interop = interop;
+        _expectedVersion = expectedVersion;
+    }
+
+    public NdiRuntimeProbeResult Probe()
+    {
+        var detected = _interop.GetRuntimeVersion();
+        return string.Equals(detected, _expectedVersion, StringComparison.Ordinal)
+            ? new NdiRuntimeProbeResult.Match(detected)
+            : new NdiRuntimeProbeResult.Mismatch(detected, _expectedVersion);
+    }
+}

src/tests/TeamsISO.Engine.Tests/Interop/NdiRuntimeProbeTests.cs

@@ -0,0 +1,32 @@
+using TeamsISO.Engine.Interop;
+using TeamsISO.Engine.Tests.Fakes;
+
+namespace TeamsISO.Engine.Tests.Interop;
+
+public class NdiRuntimeProbeTests
+{
+    [Fact]
+    public void Probe_VersionsMatch_ReturnsMatch()
+    {
+        var interop = new FakeNdiInterop { RuntimeVersion = "6.0.0" };
+        var probe = new NdiRuntimeProbe(interop, expectedVersion: "6.0.0");
+
+        var result = probe.Probe();
+
+        result.Should().BeOfType<NdiRuntimeProbeResult.Match>();
+    }
+
+    [Fact]
+    public void Probe_VersionsDiffer_ReturnsMismatchWithBoth()
+    {
+        var interop = new FakeNdiInterop { RuntimeVersion = "5.6.0" };
+        var probe = new NdiRuntimeProbe(interop, expectedVersion: "6.0.0");
+
+        var result = probe.Probe();
+
+        result.Should().BeOfType<NdiRuntimeProbeResult.Mismatch>();
+        var mismatch = (NdiRuntimeProbeResult.Mismatch)result;
+        mismatch.Detected.Should().Be("5.6.0");
+        mismatch.Expected.Should().Be("6.0.0");
+    }
+}