probe(physics): ACDREAM_PROBE_STEP_HEIGHTS — three readings along #338's chain

The live reading of 0.400 says the controller held its default at that
instant, not why. Two very different causes produce it: the
Setup-derived prepare/publish path never runs for the local player, or
it runs and a later writer clobbers the result. Fixing without knowing
which is a coin flip.

One reading at each hop — prepare (Setup value computed and scaled),
publish (assigned to the controller), resolve (what the resolver is
actually handed) — with a decision table on the flag mapping each
pattern to its cause, including the 0.000 case that would mean a null
Setup took the retail dummy path.

Edge-triggered per site, so the per-tick resolve site prints once per
distinct pair and cannot drown the two one-shot sites it exists to be
compared against. Prepare prints the raw authored pair beside the
scaled one, so a surprise separates wrong-Setup from wrong-scale
without a second run.

Lives in PhysicsDiagnostics per code-structure rule 5 rather than as
per-call-site env reads. Zero cost when off.

Suite 11,231 passed / 4 skipped / 0 failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/AcDream.Runtime/Physics/RuntimeSetPositionMoverPreparation.cs

@@ -180,6 +180,15 @@ internal static class RuntimeSetPositionMoverPreparer
         float stepUp = setup is not null ? setup.StepUpHeight * scale : 0f;
         float stepDown = setup is not null ? setup.StepDownHeight * scale : 0f;
 
+        // #338 (TEMPORARY): first of three readings along the chain. Prints
+        // the raw authored pair alongside the scaled one, so a surprise here
+        // separates "wrong Setup" from "wrong scale" without a second run.
+        PhysicsDiagnostics.LogStepHeights(
+            "prepare", stepUp, stepDown,
+            setup is not null
+                ? $"authored=({setup.StepUpHeight:F3},{setup.StepDownHeight:F3}) scale={scale:F3}"
+                : "setup=NULL (retail dummy path, exact zero steps)");
+
         EntityCollisionFlags collisionFlags =
             EntityCollisionFlagsExt.FromPwdBitfield(
                 record.Snapshot.ObjectDescriptionFlags ?? 0u);