feat(selection): port retail polygon picking and vivid marker

Replace the projected Setup-sphere rectangle and independent physics-wall ray with retail's render-coupled picker: only visible server-object parts participate, each exact drawing sphere broad-phases the camera-eye ray, and first-in-DAT-order visual polygon hits globally outrank sphere fallbacks.

Replace the devtools-only procedural triangles with the retained gameplay VividTargetIndicator using retail client-enum surfaces 1..4, radar-blip colorization, Setup selection-sphere framing, and the exact eight-pixel viewport clamp.

Release build succeeds with zero warnings and all 5,886 tests pass with five intentional skips.

Co-authored-by: OpenAI Codex <codex@openai.com>

tests/AcDream.Core.Tests/Selection/RetailWorldPickerTests.cs

@@ -0,0 +1,173 @@
+using System.Numerics;
+using AcDream.Core.Selection;
+
+namespace AcDream.Core.Tests.Selection;
+
+public sealed class RetailWorldPickerTests
+{
+    [Fact]
+    public void BuildRayStartsAtCameraViewpointRatherThanNearPlane()
+    {
+        var eye = new Vector3(10f, 20f, 30f);
+        Matrix4x4 view = Matrix4x4.CreateLookAt(eye, eye - Vector3.UnitZ, Vector3.UnitY);
+        Matrix4x4 projection = Matrix4x4.CreatePerspectiveFieldOfView(
+            MathF.PI / 3f, 4f / 3f, 0.1f, 1000f);
+
+        var ray = WorldPicker.BuildRay(400f, 300f, 800f, 600f, view, projection);
+
+        Assert.True(Vector3.Distance(eye, ray.Origin) < 0.0001f);
+        Assert.True(Vector3.Distance(-Vector3.UnitZ, ray.Direction) < 0.0001f);
+    }
+
+    [Fact]
+    public void PolygonHitGloballyBeatsNearerSphereFallback()
+    {
+        var sphereOnly = Part(1u, z: -3f, polygons: []);
+        var polygon = Part(2u, z: -8f, polygons: [SquareAtLocalZ(0f)]);
+
+        RetailSelectionHit? hit = RetailWorldPicker.Pick(
+            Vector3.Zero, -Vector3.UnitZ, [sphereOnly, polygon]);
+
+        Assert.NotNull(hit);
+        Assert.Equal(2u, hit.Value.ServerGuid);
+        Assert.True(hit.Value.PolygonHit);
+    }
+
+    [Fact]
+    public void SphereIsUsedOnlyWhenNoVisiblePolygonHits()
+    {
+        var part = Part(0xABCDu, z: -5f, polygons: []);
+
+        RetailSelectionHit? hit = RetailWorldPicker.Pick(
+            Vector3.Zero, -Vector3.UnitZ, [part]);
+
+        Assert.NotNull(hit);
+        Assert.Equal(0xABCDu, hit.Value.ServerGuid);
+        Assert.False(hit.Value.PolygonHit);
+        Assert.Equal(3d, hit.Value.Distance, 4);
+    }
+
+    [Fact]
+    public void StopsAtFirstHitPolygonInDatOrderForEachPart()
+    {
+        var datOrdered = Part(
+            10u,
+            z: 0f,
+            polygons: [SquareAtLocalZ(-10f), SquareAtLocalZ(-5f)],
+            sphereCenter: new Vector3(0f, 0f, -7.5f),
+            sphereRadius: 5f);
+        var competitor = Part(20u, z: -7f, polygons: [SquareAtLocalZ(0f)]);
+
+        RetailSelectionHit? hit = RetailWorldPicker.Pick(
+            Vector3.Zero, -Vector3.UnitZ, [datOrdered, competitor]);
+
+        // Scanning all polygons would incorrectly give guid 10 at 5 m. Retail
+        // accepts its first DAT-order hit at 10 m, so guid 20 wins at 7 m.
+        Assert.NotNull(hit);
+        Assert.Equal(20u, hit.Value.ServerGuid);
+    }
+
+    [Fact]
+    public void SingleSidedPolygonRejectsItsBackFace()
+    {
+        var front = new RetailSelectionPart(
+            1u,
+            0,
+            Matrix4x4.Identity,
+            new RetailSelectionMesh(
+                new Vector3(0f, 0f, -5f), 2f,
+                [SquareAtLocalZ(-5f, singleSided: true)]));
+
+        RetailSelectionHit? backHit = RetailWorldPicker.Pick(
+            new Vector3(0f, 0f, -10f), Vector3.UnitZ, [front]);
+
+        Assert.NotNull(backHit); // drawing sphere remains the retail fallback
+        Assert.False(backHit.Value.PolygonHit);
+    }
+
+    [Fact]
+    public void InverseScaledPartPreservesWorldDistance()
+    {
+        var transform = Matrix4x4.CreateScale(2f)
+            * Matrix4x4.CreateTranslation(0f, 0f, -10f);
+        var part = new RetailSelectionPart(
+            3u,
+            0,
+            transform,
+            new RetailSelectionMesh(Vector3.Zero, 1f, [SquareAtLocalZ(0f)]));
+
+        RetailSelectionHit? hit = RetailWorldPicker.Pick(
+            Vector3.Zero, -Vector3.UnitZ, [part]);
+
+        Assert.NotNull(hit);
+        Assert.True(hit.Value.PolygonHit);
+        Assert.Equal(10d, hit.Value.Distance, 4);
+    }
+
+    [Fact]
+    public void SkipGuidAndNonServerPartsNeverCompete()
+    {
+        RetailSelectionHit? hit = RetailWorldPicker.Pick(
+            Vector3.Zero,
+            -Vector3.UnitZ,
+            [Part(0u, -2f, [SquareAtLocalZ(0f)]), Part(7u, -4f, [SquareAtLocalZ(0f)])],
+            skipServerGuid: 7u);
+
+        Assert.Null(hit);
+    }
+
+    [Fact]
+    public void DrawingSphereRejectsRayWhichBeginsInsideLikeRetail()
+    {
+        bool hit = RetailWorldPicker.TryIntersectSphere(
+            Vector3.Zero, Vector3.UnitX, Vector3.Zero, 2f, out _);
+
+        Assert.False(hit);
+    }
+
+    [Fact]
+    public void ConvexEdgeTestRejectsAConcaveNotchRatherThanUsingEvenOddFill()
+    {
+        var concave = new RetailSelectionPolygon(
+            [
+                new(-2f, -2f, -5f),
+                new( 2f, -2f, -5f),
+                new( 2f,  2f, -5f),
+                new( 0f,  0f, -5f),
+                new(-2f,  2f, -5f),
+            ],
+            SingleSided: false);
+
+        bool hit = RetailWorldPicker.TryIntersectPolygon(
+            new Vector3(0f, 1f, 0f), -Vector3.UnitZ, concave, out _);
+
+        Assert.False(hit);
+    }
+
+    private static RetailSelectionPart Part(
+        uint guid,
+        float z,
+        IReadOnlyList<RetailSelectionPolygon> polygons,
+        Vector3? sphereCenter = null,
+        float sphereRadius = 2f)
+        => new(
+            guid,
+            0,
+            Matrix4x4.CreateTranslation(0f, 0f, z),
+            new RetailSelectionMesh(
+                sphereCenter ?? Vector3.Zero,
+                sphereRadius,
+                polygons));
+
+    private static RetailSelectionPolygon SquareAtLocalZ(
+        float z,
+        bool singleSided = false)
+        => new(
+            [
+                new Vector3(-1f, -1f, z),
+                new Vector3( 1f, -1f, z),
+                new Vector3( 1f,  1f, z),
+                new Vector3(-1f,  1f, z),
+            ],
+            singleSided);
+}