fix(perception): stabilize replay body frame

docs/adr/0040-dual-evidence-replay-threat-boundary.md

@@ -17,6 +17,13 @@ qualified LiDAR-to-body mount. A recorded threat experiment therefore needs an
 explicit virtual geometry without weakening the physical rig contract in ADR
 0035.
 
+The first M4.6 implementation incorrectly treated the instantaneous LiDAR frame
+as the virtual body frame. The K1 calibration proves that camera-forward is near
+LiDAR `-Y`, not `+X`, and the handheld pose contains real roll and pitch. That
+made the replay corridor approximately 90 degrees off the route and rotated the
+SLAM world with the operator's hand. Result `m4-threat-replay-7e1613...` is
+superseded and is not admissible M4.6 evidence.
+
 ## Decision
 
 Mission Core threat assessment consumes two independent evidence paths:
@@ -48,6 +55,26 @@ only with `replay-simulated` authority. They do not populate or qualify
 `missioncore.rig-geometry/v1`, and they cannot support physical collision,
 navigation, safety or actuation claims.
 
+The virtual collision frame is a gravity-stable `base_footprint`, not the
+instantaneous sensor frame:
+
+- the K1 vendor SLAM map remains the stable world in which mapped points live;
+- the rolling local-surface model supplies only the vertical ground origin and
+  a quality check, not a permanent level-world assumption;
+- forward is the smoothed SLAM trajectory tangent and is independently checked
+  against the calibrated camera optical axis;
+- unavailable height, excessive local slope or camera/route disagreement makes
+  that frame unqualified instead of silently rotating the corridor;
+- a mounted vehicle replaces this replay-only derivation with one measured,
+  rigid `T_body_from_sensor`; the detector, obstacle map and threat policy do not
+  change.
+
+The sensor may therefore be mounted at a non-level angle or noncentral position
+as long as it is rigid and its one-time body extrinsic is known. Vehicle roll
+and pitch do not corrupt the SLAM map; a future 3D swept-volume planner may use
+`base_link`, while the current 2D corridor remains explicitly tied to
+`base_footprint`.
+
 ## Evidence and presentation
 
 The accepted replay must publish immutable frame, fixture, report and visual
@@ -57,6 +84,8 @@ ledgers. Visual evidence uses the common LAB viewer and reusable renderers:
 - exact camera samples with metric range or explicit missing range;
 - synchronized point cloud, occupied cells, virtual body and corridor in 3D and
   plan view;
+- mandatory regression frames `138` and `274`, which exposed the original
+  sensor/body-axis failure;
 - visible threat/not-threat/unknown and `replay-simulated` authority.
 
 Visuals are an inspection surface, not ground truth. Independent object-centric