docs(memory): record the vehicle settle fix and the failed root-bone experiment

MEMORY.md

@@ -1158,3 +1158,27 @@ Historical task context from 2026-11-09/10; later vehicle findings above may sup
 - The hot-hatch skeletal mesh now imports (403 x 148 x 158 cm), but the mesh is rolled (height Y,
   width Z) while the armature is correct - the MESH vertices are exported raw (identity) while the
   ARMATURE is baked with the FBX conversion, the same mesh-vs-armature split as before.
+
+## 2026-11-10 — Vehicle settles (float 33 m -> 6 cm); drive still ~0
+
+- **Two real fixes** (commit `319096d`):
+  1. The skeletal mesh imports ROLLED (height along Y, width along Z) while the armature is
+     unrolled. The chassis box must therefore be built with swapped axes (`Box.Y = Extent.Z*1.8`,
+     `Box.Z = Extent.Y*0.55`) and centred at the rolled mesh's mid-height (`Box.Center.Z =
+     Bounds.Origin.Y`). This is what settled the car at Z 6 cm (was floating at 33 m).
+  2. A diagnostic `if (SettleElapsed > 2.5f) Mover->SetComponentTickEnabled(false)` was firing for
+     every vehicle (not just zero-wheel ones) and cut the drive test (throttle 1-4 s). Now gated
+     on `Wheels.Num() == 0`.
+- **Experiment that FAILED and was reverted**: moving the root bone to the centre of mass in
+  `vehicle_from_template.py` (root at `body.bound_box` centre) puts the wheel bones at NEGATIVE Z
+  (-54 cm below root) and the vehicle then FLOATS at spawn height (stays Z 304, never falls).
+  So the Chaos suspension in this rig wants a POSITIVE rest position (wheel bone above the root
+  bone). Root bone stays grounded at (0,0,0); the box offset to centre of mass is done in C++.
+- **Remaining**: drive test reports `speed=1 cm/s` (no forward motion) and `travelled ~56 m` - a
+  horizontal drift during the fall. Wheels rest ~2 cm above the ground (wheel bone Z +34 vs wheel
+  radius 33) because the suspension rest position is measured against the root bone while the box
+  sits at +76. Next: make the wheels actually contact (align wheel radius to the bone, or correct
+  the rest position for the box offset) before re-testing direction.
+- `GetWheelRestingPosition` = `LocateBoneOffset(BoneName, WheelClass.Offset + AdditionalOffset)`,
+  which is the wheel bone position relative to the ROOT BODY BONE - it does NOT account for
+  `Box.Center`. That offset is the root of the drive gap.