feat(runtime): own SetPosition collision reports

tests/AcDream.App.Tests/Runtime/RuntimePhysicsOwnershipTests.cs

@@ -63,6 +63,73 @@ public sealed class RuntimePhysicsOwnershipTests
             StringComparison.Ordinal);
     }
 
+    [Fact]
+    public void GraphicalAndHeadlessHostsBorrowOneRuntimeCollisionAuthority()
+    {
+        string root = FindRepositoryRoot();
+        string appRoot = Path.Combine(root, "src", "AcDream.App");
+        string headlessRoot = Path.Combine(root, "src", "AcDream.Headless");
+        string gameWindow = File.ReadAllText(Path.Combine(
+            appRoot,
+            "Rendering",
+            "GameWindow.cs"));
+        string headlessProjection = File.ReadAllText(Path.Combine(
+            headlessRoot,
+            "Hosting",
+            "HeadlessSessionWorldProjection.cs"));
+        string productionHosts = string.Join(
+            "\n",
+            Directory.EnumerateFiles(
+                    appRoot,
+                    "*.cs",
+                    SearchOption.AllDirectories)
+                .Concat(Directory.EnumerateFiles(
+                    headlessRoot,
+                    "*.cs",
+                    SearchOption.AllDirectories))
+                .Select(File.ReadAllText));
+
+        Assert.Contains(
+            "private RuntimeEntityObjectLifetime _runtimeEntityObjects =>",
+            gameWindow,
+            StringComparison.Ordinal);
+        Assert.Contains(
+            "_runtime.EntityObjects;",
+            gameWindow,
+            StringComparison.Ordinal);
+        Assert.Contains(
+            "_runtimeEntityObjects.Physics",
+            gameWindow,
+            StringComparison.Ordinal);
+        Assert.Contains(
+            "private readonly GameRuntime _runtime;",
+            headlessProjection,
+            StringComparison.Ordinal);
+        Assert.Contains(
+            "_runtime.EntityObjects.Physics",
+            headlessProjection,
+            StringComparison.Ordinal);
+
+        // Hosts may project reports later, but they must never own a second
+        // collision table or reproduce Runtime's return/error heuristic.
+        Assert.DoesNotContain(
+            "new RuntimeCollisionReportingState",
+            productionHosts,
+            StringComparison.Ordinal);
+        Assert.DoesNotContain(
+            "class RuntimeCollisionReportingState",
+            productionHosts,
+            StringComparison.Ordinal);
+        Assert.DoesNotContain(
+            "HandleSetPositionCollisions(",
+            productionHosts,
+            StringComparison.Ordinal);
+        Assert.DoesNotContain(
+            "CollidingWithEnvironment",
+            productionHosts,
+            StringComparison.Ordinal);
+    }
+
     [Fact]
     public void AppPhysicsFilesArePresentationAndPreparedAssetAdapters()
     {