fix(combat): track targets with retail camera

Port ClientCombatSystem's Keep in View consumer through CameraSet's pivot-to-target boom heading, including the transformed half-metre target offset and melee/missile validity gates. Preserve the existing stateful chase damping and collision architecture, with conformance coverage and named-retail pseudocode.

Co-Authored-By: Codex <codex@openai.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -8415,13 +8415,15 @@ public sealed class GameWindow : IDisposable
             // player visibly rises in frame without the camera
             // swinging vertically (was the symptom of using raw
             // velocity-vector heading).
+            System.Numerics.Vector3? trackedCombatTarget = GetCombatCameraTargetPoint();
             _retailChaseCamera!.Update(result.RenderPosition, _playerController.Yaw,
                 playerVelocity:     _playerController.BodyVelocity,
                 isOnGround:         result.IsOnGround,
                 contactPlaneNormal: _playerController.ContactPlane.Normal,
                 dt:                 (float)dt,
                 cellId:             _playerController.CellId,
-                selfEntityId:       _playerController.LocalEntityId);
+                selfEntityId:       _playerController.LocalEntityId,
+                trackedTargetPoint: trackedCombatTarget);
 
             // Send outbound movement messages to the live server.
             if (_liveSession is not null)
@@ -12021,6 +12023,26 @@ public sealed class GameWindow : IDisposable
         return SelectClosestCombatTarget(showToast: false);
     }
 
+    /// <summary>
+    /// Resolves retail's combat-camera target. ClientCombatSystem::
+    /// UpdateTargetTracking (0x0056A950) enables CameraSet::TrackTarget only
+    /// for melee/missile combat with the option enabled and a valid attack
+    /// target. TrackTarget applies target-local offset (0,0,0.5).
+    /// </summary>
+    private System.Numerics.Vector3? GetCombatCameraTargetPoint()
+    {
+        if (!_persistedGameplay.ViewCombatTarget
+            || !AcDream.Core.Combat.CombatInputPlanner.SupportsTargetedAttack(Combat.CurrentMode)
+            || _selection.SelectedObjectId is not uint selected
+            || !IsLiveCreatureTarget(selected)
+            || !_entitiesByServerGuid.TryGetValue(selected, out var target))
+            return null;
+
+        return target.Position
+            + System.Numerics.Vector3.Transform(
+                new System.Numerics.Vector3(0f, 0f, 0.5f), target.Rotation);
+    }
+
     // ============================================================
     // Phase B.4b — outbound Use handler. Wires three input actions
     // (LMB click select, LMB-double-click select+use, R hotkey

src/AcDream.App/Rendering/RetailChaseCamera.cs

@@ -143,28 +143,31 @@ public sealed class RetailChaseCamera : ICamera
         Vector3 contactPlaneNormal,
         float dt,
         uint cellId = 0,
-        uint selfEntityId = 0)
+        uint selfEntityId = 0,
+        Vector3? trackedTargetPoint = null)
     {
         // 1. Push velocity into 5-frame ring, get average.
         PushVelocity(_velocityRing, ref _velocityCount, playerVelocity);
         Vector3 avgVel = AverageVelocity(_velocityRing, _velocityCount);
 
-        // 2. Heading vector — player's facing projected onto the contact
-        //    plane (grounded) or world XY (airborne). See ComputeHeading
-        //    doc + retail decomp :95644-95795 for why this is facing-based
-        //    rather than velocity-based.
-        Vector3 heading = ComputeHeading(
-            avgVel,
-            playerYaw + YawOffset,
-            isOnGround,
-            contactPlaneNormal,
-            CameraDiagnostics.AlignToSlope);
+        // 2. Heading vector. TrackTarget uses the pivot-to-target direction;
+        //    otherwise this is the player's facing projected onto the contact
+        //    plane (grounded) or world XY (airborne). See named retail
+        //    CameraSet::TrackTarget 0x00458280 and CameraManager::UpdateCamera
+        //    0x00456826-0x00456915.
+        Vector3 pivotWorld = playerPosition + new Vector3(0f, 0f, PivotHeight);
+        Vector3 heading = ComputeTrackedHeading(pivotWorld, trackedTargetPoint)
+            ?? ComputeHeading(
+                avgVel,
+                playerYaw + YawOffset,
+                isOnGround,
+                contactPlaneNormal,
+                CameraDiagnostics.AlignToSlope);
 
         // 3. Orthonormal heading-frame basis.
         var (forward, _, up) = BuildBasis(heading);
 
         // 4. Target pose.
-        Vector3 pivotWorld = playerPosition + new Vector3(0f, 0f, PivotHeight);
         float   horizontal = Distance * MathF.Cos(Pitch);
         float   vertical   = Distance * MathF.Sin(Pitch);
         // viewer_offset = -horizontal along forward + vertical along up.
@@ -359,6 +362,24 @@ public sealed class RetailChaseCamera : ICamera
         return Vector3.Normalize(projected);
     }
 
+    /// <summary>
+    /// Port of the LOOK_AT_OBJECT direction contribution in retail
+    /// CameraManager::UpdateCamera (0x00456826-0x00456915). The caller
+    /// supplies the transformed world-space target point, including retail's
+    /// local (0,0,0.5) target offset. A coincident point cannot define a
+    /// heading, so the ordinary player-facing path remains active.
+    /// </summary>
+    internal static Vector3? ComputeTrackedHeading(Vector3 pivotWorld, Vector3? trackedTargetPoint)
+    {
+        if (trackedTargetPoint is not Vector3 targetPoint)
+            return null;
+
+        Vector3 towardTarget = targetPoint - pivotWorld;
+        return towardTarget.LengthSquared() < 1e-8f
+            ? null
+            : Vector3.Normalize(towardTarget);
+    }
+
     /// <summary>
     /// Build an orthonormal basis with <c>forward = heading</c>. World
     /// up is <c>(0, 0, 1)</c>; if <c>heading</c> is near-parallel to it