fix(physics): TS-46 - seed the sweep from the Setup's own sphere list

Campaign P Slice P3 item 1. Retail CPhysicsObj::transition (0x00512dc0)
seeds the collision sweep from CPartArray::GetSphere (the Setup's own
<=2-sphere list, each origin+radius scaled by m_scale) via
SPHEREPATH::init_sphere (0x0050c670) -- not from a symmetric two-scalar
(radius, height) capsule reconstruction. The human Setup 0x02000001's
authored spheres are (0,0,0.475) r=.48 and (0,0,1.350) r=.48; the old
reconstruction from (0.48, 1.835) produced (0,0,0.48) + (0,0,1.355), a
5 mm head-center offset the TS-46 register row documented as a residual.

Port:
- SpherePath.InitPath gains a sphere-list overload (ImmutableArray<
  FlatCollisionSphere>, scale) sharing a new InitPathCore with the
  existing (radius, height) overload, which is now the degenerate
  2-scalar case of the same code -- byte-for-byte unchanged, so every
  captured-fixture replay (CellarUpTrajectoryReplayTests,
  DoorBugTrajectoryReplayTests, CellarLipWedgeTests) keeps passing
  unmodified.
- PhysicsEngine.ResolveWithTransition gains optional sphereList/
  sphereScale parameters; empty/default preserves the legacy scalar
  path for every pre-existing caller.
- LiveEntityMotionRuntimeController.GetSetupMoverShape is a new sibling
  of GetSetupCylinder (left untouched) that resolves the Setup's own
  sphere list plus Setup-derived step-up/step-down
  (CPartArray::GetStepUpHeight/GetStepDownHeight, 0x005180d0/0x005180f0,
  x ObjScale, 0.4 m fallback matching the pre-existing literal).
- Threaded through PlayerMovementController (both resolve call sites,
  new SphereList property set by PlayerModeController.ApplyStepHeights
  and the Headless world projection), RuntimeRemotePhysicsUpdater
  (Tick + TickHidden), and RuntimeOrdinaryPhysicsUpdater.TryBegin.
  Remote/ordinary step heights are now Setup-derived instead of a
  hardcoded 0.4f literal. Projectile and camera-probe sweeps are
  untouched (already single-sphere-exact).
- PlayerModeController.ApplyStepHeights also now applies the x ObjScale
  multiply to the player's own step heights (previously only the
  remote/ordinary paths did), closing an adjacent gap the P3 research
  flagged.

Ts46SphereListConformanceTests proves the sphere-list overload sees the
exact dat spheres (not the reconstruction), that the scalar overload is
unchanged, and that ResolveWithTransition's sphereList parameter
actually drives the sweep (a decoy-scalar control pair using a
head-height obstacle sphere).

Register: TS-46 retired (both residuals it named are closed); header
count corrected to 40 active TS rows.

dotnet build + dotnet test (Core.Tests 3991/2 skip, Runtime.Tests
425/0, App.Tests 3968/3 skip, complete solution build) all green.

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

src/AcDream.App/Physics/LiveEntityMotionRuntimeController.cs

@@ -1,3 +1,4 @@
+using System.Collections.Immutable;
 using AcDream.App.Interaction;
 using AcDream.App.Rendering;
 using AcDream.App.World;
@@ -283,6 +284,45 @@ internal sealed class LiveEntityMotionRuntimeController
         return (setup.Radius * scale, setup.Height * scale);
     }
 
+    /// <summary>
+    /// TS-46 (2026-07-30) sibling of <see cref="GetSetupCylinder"/>: the
+    /// Setup's own ≤2-sphere list (retail <c>CPhysicsObj::transition</c>
+    /// 0x00512dc0 → <c>SPHEREPATH::init_sphere</c> 0x0050c670) plus
+    /// Setup-derived step-up/step-down (<c>CPartArray::GetStepUpHeight</c>/
+    /// <c>GetStepDownHeight</c>, 0x005180d0/0x005180f0 — both scaled by the
+    /// object's own ObjScale, matching the existing 0.4 m literal fallback
+    /// the remote/ordinary callers already carried). <see cref="GetSetupCylinder"/>
+    /// is deliberately UNTOUCHED — its callers want the single-radius/height
+    /// CYLINDER for sticky/moveto math, not the collision sweep shape.
+    /// Returns an empty sphere list (and the 0.4 m fallbacks) when the
+    /// entity has no resolvable/prepared Setup, or when the Setup carries no
+    /// sphere rows — <see cref="PhysicsEngine.ResolveWithTransition"/>'s
+    /// <c>sphereList</c> parameter treats empty as "use the legacy
+    /// two-scalar reconstruction", so this degrades gracefully rather than
+    /// degenerating the sweep.
+    /// </summary>
+    public (ImmutableArray<FlatCollisionSphere> Spheres, float Scale, float StepUpHeight, float StepDownHeight)
+        GetSetupMoverShape(uint serverGuid, AcDream.Core.World.WorldEntity entity)
+    {
+        FlatSetupCollision? setup =
+            _physicsDataCache.GetFlatSetup(entity.SourceGfxObjOrSetupId);
+        if (setup is null)
+            return (ImmutableArray<FlatCollisionSphere>.Empty, 1f, 0.4f, 0.4f);
+
+        // Same scale resolution as GetSetupCylinder (see its own comment):
+        // the spawn record's ObjScale is authoritative for live spawns; a
+        // non-spawn entity (scenery) falls back to WorldEntity.Scale.
+        float scale =
+            _liveEntities.Snapshots.TryGetValue(serverGuid, out var sp)
+                && sp.ObjScale is { } objScale && objScale > 0f
+            ? objScale
+            : (entity.Scale > 0f ? entity.Scale : 1f);
+
+        float stepUp = setup.StepUpHeight > 0f ? setup.StepUpHeight * scale : 0.4f;
+        float stepDown = setup.StepDownHeight > 0f ? setup.StepDownHeight * scale : 0.4f;
+        return (setup.Spheres, scale, stepUp, stepDown);
+    }
+
     // #184 Slice 2a: ApplyPositionManagerDelta + SyncRemoteShadowToBody moved to
     // AcDream.App.Physics.RemotePhysicsUpdater. ApplyPositionManagerDelta had no
     // caller outside the DR tick; SyncRemoteShadowToBody is now called back via