feat(render): Phase A8.F — PhysicsCameraCollisionProbe (swept-sphere eye via ResolveWithTransition)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/AcDream.App/Rendering/ICameraCollisionProbe.cs

@@ -0,0 +1,20 @@
+using System.Numerics;
+
+namespace AcDream.App.Rendering;
+
+/// <summary>
+/// Sweeps a small sphere from the camera pivot (player head) toward the
+/// desired eye and returns the stopped (non-penetrating) eye. The seam that
+/// lets <see cref="RetailChaseCamera"/> collide its eye without depending on
+/// the physics engine directly (and stay unit-testable with a fake).
+/// </summary>
+public interface ICameraCollisionProbe
+{
+    /// <summary>
+    /// Roll a collision sphere from <paramref name="pivot"/> to
+    /// <paramref name="desiredEye"/>; return the position it reaches without
+    /// penetrating geometry. Returns <paramref name="desiredEye"/> unchanged
+    /// when nothing blocks the path or when <paramref name="cellId"/> is 0.
+    /// </summary>
+    Vector3 SweepEye(Vector3 pivot, Vector3 desiredEye, uint cellId, uint selfEntityId);
+}