Implement engine-bridge PoC v1 (#9)

- Add Recordingtest.EngineBridge library (IEngineSnapshot, HmEgSnapshot
  skeleton, MetadataLoader, CandidateFinder, CatalogWriter).
- Add Recordingtest.EngineBridge.Probe console exe that dumps
  hmeg-types.json and hmeg-candidates.json to docs/engine-catalog.
- Add Recordingtest.EngineBridge.Tests (xUnit, 6 tests).
- Add probe design doc with plugin-masquerade recommendation.
- Static analysis only; SUT is never executed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/Recordingtest.EngineBridge.Tests/EngineBridgeTests.cs

@@ -0,0 +1,135 @@
+using System.Reflection;
+using System.Text.Json;
+using Recordingtest.EngineBridge;
+using Xunit;
+
+namespace Recordingtest.EngineBridge.Tests;
+
+public sealed class EngineBridgeTests
+{
+    private static readonly Lazy<string?> SutRootLazy = new(FindSutRoot);
+    private static string? SutRoot => SutRootLazy.Value;
+    private static bool SutAvailable => SutRoot != null;
+
+    private static readonly string[] TargetAssemblies =
+    {
+        "HmEG.dll",
+        "HmGeometry.dll",
+        "HmGeometry.V2.dll",
+        "HmTriangle.dll",
+        "EditorCore.dll",
+        "Editor02.HmEGAppManager.dll",
+        "Editor03.PluginInterface.dll",
+    };
+
+    private static string? FindSutRoot()
+    {
+        var dir = new DirectoryInfo(AppContext.BaseDirectory);
+        for (int i = 0; i < 10 && dir != null; i++)
+        {
+            var candidate = Path.Combine(dir.FullName, "EG-BIM Modeler");
+            if (Directory.Exists(candidate) && File.Exists(Path.Combine(candidate, "HmEG.dll")))
+                return candidate;
+            dir = dir.Parent;
+        }
+        return null;
+    }
+
+    [Fact]
+    public void MetadataLoader_LoadsHmegAssembly_WithoutExecution()
+    {
+        if (!SutAvailable) { Assert.True(true, "SUT not available — skipped"); return; }
+
+        // MetadataLoadContext is pure metadata: it never runs type initializers
+        // or any user code from the loaded assembly. The fact that we can load
+        // HmEG.dll (which would otherwise need SharpDX/WPF at runtime) and
+        // enumerate DefinedTypes without a TypeInitializationException is the
+        // observable evidence of that guarantee.
+        using var loader = new MetadataLoader(SutRoot!);
+        var types = loader.LoadTypes(new[] { "HmEG.dll" }).ToList();
+        Assert.True(types.Count > 0);
+    }
+
+    [Fact]
+    public void CandidateFinder_FindsSelectionRelatedTypes()
+    {
+        if (!SutAvailable) { Assert.True(true, "SUT not available — skipped"); return; }
+
+        using var loader = new MetadataLoader(SutRoot!);
+        var types = loader.LoadTypes(TargetAssemblies).ToList();
+        var candidates = CandidateFinder.Find(types);
+        Assert.Contains(candidates, c => c.Category == "select");
+    }
+
+    [Fact]
+    public void CatalogSerializer_OutputsSorted_Idempotent()
+    {
+        if (!SutAvailable) { Assert.True(true, "SUT not available — skipped"); return; }
+
+        using var loader = new MetadataLoader(SutRoot!);
+        var types = loader.LoadTypes(new[] { "HmEG.dll" }).ToList();
+        var candidates = CandidateFinder.Find(types);
+
+        var tmp1 = Path.Combine(Path.GetTempPath(), "eb-cand-1-" + Guid.NewGuid().ToString("N") + ".json");
+        var tmp2 = Path.Combine(Path.GetTempPath(), "eb-cand-2-" + Guid.NewGuid().ToString("N") + ".json");
+        try
+        {
+            CatalogWriter.WriteCandidates(tmp1, candidates);
+            CatalogWriter.WriteCandidates(tmp2, candidates);
+            Assert.Equal(File.ReadAllBytes(tmp1), File.ReadAllBytes(tmp2));
+        }
+        finally
+        {
+            File.Delete(tmp1);
+            File.Delete(tmp2);
+        }
+    }
+
+    [Fact]
+    public void HmEgSnapshot_DefaultInstance_ThrowsNotImplemented()
+    {
+        var s = new HmEgSnapshot();
+        Assert.Throws<NotImplementedException>(() => _ = s.SelectedObjectIds);
+        Assert.Throws<NotImplementedException>(() => _ = s.Camera);
+        Assert.Throws<NotImplementedException>(() => _ = s.Scene);
+        Assert.Throws<NotImplementedException>(() => _ = s.IsRenderComplete);
+    }
+
+    [Fact]
+    public void CandidateCategories_AllFourPresent()
+    {
+        if (!SutAvailable) { Assert.True(true, "SUT not available — skipped"); return; }
+
+        using var loader = new MetadataLoader(SutRoot!);
+        var types = loader.LoadTypes(TargetAssemblies).ToList();
+        var candidates = CandidateFinder.Find(types);
+
+        foreach (var cat in new[] { "select", "camera", "scene", "render" })
+        {
+            Assert.True(candidates.Any(c => c.Category == cat), $"category '{cat}' missing");
+        }
+    }
+
+    [Fact]
+    public void HmEgSnapshot_Constants_MatchCatalog()
+    {
+        if (!SutAvailable) { Assert.True(true, "SUT not available — skipped"); return; }
+
+        using var loader = new MetadataLoader(SutRoot!);
+        var types = loader.LoadTypes(TargetAssemblies).ToList();
+        var candidates = CandidateFinder.Find(types);
+
+        // HmEgAssemblyHint ("HmEG") should be a prefix of at least one loaded assembly.
+        var asmNames = types.Select(t => t.Assembly.GetName().Name ?? "").Distinct().ToList();
+        Assert.Contains(asmNames, a => a.StartsWith(HmEgSnapshot.HmEgAssemblyHint, StringComparison.Ordinal));
+
+        // EditorManagerTypeHint ("HmEGAppManager") should appear in at least one candidate TypeName OR type entry.
+        var appearsInCandidates = candidates.Any(c =>
+            c.TypeName.Contains(HmEgSnapshot.EditorManagerTypeHint, StringComparison.Ordinal));
+        var appearsInTypes = types.Any(t =>
+            (t.FullName ?? t.Name).Contains(HmEgSnapshot.EditorManagerTypeHint, StringComparison.Ordinal) ||
+            (t.Assembly.GetName().Name ?? "").Contains(HmEgSnapshot.EditorManagerTypeHint, StringComparison.Ordinal));
+        Assert.True(appearsInCandidates || appearsInTypes,
+            $"EditorManagerTypeHint '{HmEgSnapshot.EditorManagerTypeHint}' not found in catalog");
+    }
+}