feat(physics): A6.P1 — add LogPushBackAdjust helper

One-line per-call emission helper for the AdjustSphereToPlane
instrumentation site. Direct field-for-field paired comparison to
retail's CPolygon::adjust_sphere_to_plane breakpoint.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.Core/Physics/PhysicsDiagnostics.cs

@@ -304,6 +304,50 @@ public static class PhysicsDiagnostics
     public static bool ProbePushBackEnabled { get; set; } =
         Environment.GetEnvironmentVariable("ACDREAM_PROBE_PUSH_BACK") == "1";
 
+    /// <summary>
+    /// A6.P1 emission helper for the <c>AdjustSphereToPlane</c> site.
+    /// One line per call: input sphere center, plane geometry, push-back
+    /// delta, walk-interp before/after, and whether the adjust applied.
+    /// Direct paired comparison to retail's cdb breakpoint on
+    /// <c>CPolygon::adjust_sphere_to_plane</c>.
+    ///
+    /// <para>
+    /// Caller MUST guard with <c>if (!ProbePushBackEnabled) return;</c>
+    /// before computing the delta arguments — this method assumes the
+    /// caller paid that price already.
+    /// </para>
+    /// </summary>
+    public static void LogPushBackAdjust(
+        Vector3 inputCenter,
+        Vector3 outputCenter,
+        Plane   plane,
+        float   radius,
+        float   walkInterpBefore,
+        float   walkInterpAfter,
+        float   dpPos,
+        float   dpMove,
+        float   iDist,
+        bool    applied)
+    {
+        var delta = outputCenter - inputCenter;
+        float deltaMag = delta.Length();
+        var ci = System.Globalization.CultureInfo.InvariantCulture;
+        Console.WriteLine(string.Format(ci,
+            "[push-back] site=adjust_sphere " +
+            "in=({0:F4},{1:F4},{2:F4}) " +
+            "out=({3:F4},{4:F4},{5:F4}) " +
+            "delta=({6:F4},{7:F4},{8:F4}) deltaMag={9:F4} " +
+            "n=({10:F4},{11:F4},{12:F4}) d={13:F4} " +
+            "r={14:F4} winterp={15:F4}->{16:F4} " +
+            "dpPos={17:F4} dpMove={18:F4} iDist={19:F4} applied={20}",
+            inputCenter.X,  inputCenter.Y,  inputCenter.Z,
+            outputCenter.X, outputCenter.Y, outputCenter.Z,
+            delta.X,        delta.Y,        delta.Z,        deltaMag,
+            plane.Normal.X, plane.Normal.Y, plane.Normal.Z, plane.D,
+            radius, walkInterpBefore, walkInterpAfter,
+            dpPos, dpMove, iDist, applied));
+    }
+
     public static void LogCpBoolWrite(string field, bool oldValue, bool newValue)
     {
         var caller = GetCpCallerName();