test(p2): faithful cellar-lip wedge reproduction + investigation apparatus (no fix yet)

P2 / M1.5 "blocked at the last step" cellar-lip wedge. This session built a faithful
deterministic reproduction and peeled the cause through six evidence-disproven framings
to one bounded question. NO fix landed — the last layers were each disproven by evidence,
and guessing at the load-bearing collision code is the saga's failure mode.

Apparatus:
- CellarLipWedgeTests.cs + Fixtures/cellar-lip/ (3 real cell dumps + wedge-records.jsonl =
  29 captured ACDREAM_CAPTURE_RESOLVE wedge calls). Replays the exact calls + body-before
  through the lip-cell engine: all 29 reproduce at 0% advance in <200 ms. Tests are
  documents-the-bug / diagnostics (GREEN while the wedge exists).
- TEMP probes ([path5-wall]/[fw-enter]/[find-walkable] in BSPQuery; [neg-poly]/[stepsphereup]/
  [stepdown-decide]/CheckOtherCells cn/sn/negHit in TransitionTypes), gated on
  ACDREAM_PROBE_INDOOR_BSP, marked STRIP. TransitionTypes neg-poly shortcut has a reverted-fix
  comment (slide attempt didn't clear the wedge).
- tools/cdb/retail-*-trace.cdb (retail cdb traces).

Findings (handoff: docs/research/2026-06-04-p2-cellar-lip-flatfloor-cp-handoff.md, see the
"NEXT-SESSION KICKOFF" at top):
- Flat-floor contact plane is retail-faithful (v1 trace, full-file correlation). NOT the bug.
- PosHitsSphere cull sign is retail-faithful (cdb -z verified; the Binary Ninja `test ah,N; jp`
  parity-jump reads inverted — caught + reverted a wrong fix from that mis-read).
- Sphere radius correct (0.48 player / 0.30 camera probe).
- Retail connector cell 0xA9B40175 never blocks (CEnvCell::find_collisions trace: 0 Collided/Slid).
- PINNED: during the step-up's step-down, BSPQuery.FindWalkableInternal is never called for cell
  0171, so the cottage floor (poly 0x0023, Z=94) is never tested as walkable -> no contact plane
  -> step-up fails -> StepUpSlide=Collided -> wedge.

Next: trace FindEnvCollisions -> FindCollisions path dispatch for 0171 during StepDown=true (why
StepSphereDown/find_walkable is skipped), port retail, validate via CellarLipWedgeTests, regress
DoorBugTrajectoryReplayTests + visual gate.

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

src/AcDream.Core/Physics/BSPQuery.cs

@@ -1374,10 +1374,27 @@ public static class BSPQuery
         Vector3       collisionNormal,
         PhysicsEngine engine)
     {
-        if (transition.DoStepUp(collisionNormal, engine!))
+        bool stepped = transition.DoStepUp(collisionNormal, engine!);
+
+        // TEMP diagnostic (cellar-lip wedge, 2026-06-04): this is the suspected
+        // recursive step-up onto the CONNECTOR cell during the outer check_other_cells
+        // (StepUp/StepDown both false). Log which cell, the input normal, whether the
+        // climb succeeded, and the slide fallback's result. STRIP once the wedge fix lands.
+        if (PhysicsDiagnostics.ProbeIndoorBspEnabled)
+        {
+            var p = transition.SpherePath;
+            Console.WriteLine(System.FormattableString.Invariant(
+                $"[stepsphereup] cell=0x{p.CheckCellId:X8} stepUpFlag={p.StepUp} stepDownFlag={p.StepDown} n=({collisionNormal.X:F2},{collisionNormal.Y:F2},{collisionNormal.Z:F2}) stepped={stepped} pos=({p.CheckPos.X:F3},{p.CheckPos.Y:F3},{p.CheckPos.Z:F3})"));
+        }
+
+        if (stepped)
             return TransitionState.OK;
 
-        return transition.SpherePath.StepUpSlide(transition);
+        var slideRes = transition.SpherePath.StepUpSlide(transition);
+        if (PhysicsDiagnostics.ProbeIndoorBspEnabled)
+            Console.WriteLine(System.FormattableString.Invariant(
+                $"[stepsphereup] cell=0x{transition.SpherePath.CheckCellId:X8} → StepUpSlide={slideRes}"));
+        return slideRes;
     }
 
     // -------------------------------------------------------------------------
@@ -1494,6 +1511,17 @@ public static class BSPQuery
         path.NegStepUp        = stepUp;
         // ACE: path.LocalSpacePos.LocalToGlobalVec(hitPoly.Plane.Normal)
         path.NegCollisionNormal = Vector3.Transform(hitPoly.Plane.Normal, localToWorld);
+
+        // TEMP diagnostic (cellar-lip wedge, 2026-06-04): name the exact near-miss
+        // polygon (id + local normal + sides) + the foot/head mapping (stepUp) + the
+        // step-down flag, so we can tell which connector poly the step-up grazes.
+        // Gated on ACDREAM_PROBE_INDOOR_BSP. STRIP once the wedge fix lands.
+        if (PhysicsDiagnostics.ProbeIndoorBspEnabled)
+        {
+            var nl = hitPoly.Plane.Normal;
+            Console.WriteLine(System.FormattableString.Invariant(
+                $"[neg-poly] cell=0x{path.CheckCellId:X8} stepUp={stepUp} stepDownFlag={path.StepDown} poly=0x{hitPoly.Id:X4} nLocal=({nl.X:F3},{nl.Y:F3},{nl.Z:F3}) sides={hitPoly.SidesType} checkPos=({path.CheckPos.X:F3},{path.CheckPos.Y:F3},{path.CheckPos.Z:F3})"));
+        }
         return TransitionState.OK;
     }