fix(physics #145): Slice 3 — carried-anchor membership; closes the far-town cascade

The outdoor membership pick derived the landblock origin from the terrain
registry, which returns (0,0) for an UNSTREAMED neighbour — so a fresh far-town
teleport at a landblock edge marched the cell id one block per physics tick
(the cascade; the 17410 ACE rejects is its wire artifact).

Fix: thread the CARRIED cell-relative frame anchor (body.Position -
body.CellPosition.Frame.Origin) into the pick via SpherePath.CarriedBlockOrigin.
That anchor IS the true landblock world origin, correct even for an unstreamed
neighbour, so the pick re-derives the SAME (consistent) cell and never marches.
- CellTransit.FindCellSet/BuildCellSetAndPickContaining: Vector3? carriedBlockOrigin
  (null default = legacy TryGetTerrainOrigin → every existing caller/test untouched).
- PhysicsEngine.ResolveWithTransition: set the anchor from a SEEDED OUTDOOR body
  whose carried landblock matches the resolve cell (else null → legacy).
- PlayerMovementController.SetPosition: 3-arg overload seeds CellPosition from the
  wire's (cell, local) via SnapToCell; 2-arg delegates with cellLocal=pos (anchor
  (0,0,0) == legacy → zero test churn).
- GameWindow.CellLocalForSeed: the placement seam (_liveCenter used ONCE here to
  derive the cell-local; physics carries it forward without _liveCenter).
Regression: TeleportFarTownRunawayTests (south + east edge, unstreamed neighbour).
Core 1529 / App 480, zero regressions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.App/Input/PlayerMovementController.cs

@@ -792,8 +792,22 @@ public sealed class PlayerMovementController
     }
 
     public void SetPosition(Vector3 pos, uint cellId)
+        // #145: tests + legacy callers run in the world==block-local frame (no
+        // streaming center), so the cell-local seed IS the world position. This
+        // makes the carried anchor (body.Position − CellPosition.Origin) == (0,0,0),
+        // identical to the legacy Zero terrain-origin fallback → behaviour unchanged.
+        => SetPosition(pos, cellId, pos);
+
+    /// <summary>
+    /// Server-snap / teleport placement. <paramref name="cellLocal"/> is the
+    /// LANDBLOCK-relative position (the wire's local, or world − landblock origin)
+    /// which seeds the body's cell-relative <c>CellPosition</c> WITHOUT any streaming
+    /// center (#145). A teleport is a large jump, so this snaps the cell frame
+    /// directly via <c>SnapToCell</c> rather than delta-syncing through the setter.
+    /// </summary>
+    public void SetPosition(Vector3 pos, uint cellId, Vector3 cellLocal)
     {
-        _body.Position = pos;
+        _body.SnapToCell(cellId, pos, cellLocal);
         _prevPhysicsPos = pos;
         _currPhysicsPos = pos;
         UpdateCellId(cellId, "teleport");