#119-residual ROOT CAUSE: the +0.02 m render lift leaked into the portal-visibility graph - horizontal portals side-culled anyone standing on them

The live capture pinned it end to end. BuildInteriorEntitiesForStreaming
lifts the render-side cell transform +0.02 m Z (shell z-fighting vs
terrain - a DRAW concern) and passed that LIFTED transform to
BuildLoadedCell, so every plane in the visibility graph sat 2 cm high.
The portal side test's in-plane window is +-10 mm: an eye standing ON a
floor containing a HORIZONTAL portal (the tower's deck lip 010A->0107,
stair landings, cellar mouths) sits 0-10 mm above the TRUE plane = 10-20
mm BELOW the lifted plane -> outside the window -> the cell behind the
portal side-culled out of the flood. Captured live at the stair top:
root=0xAAB3010A eye z=126.803 vs the portal plane at 126.80, flood=1,
0x0107 (the whole tower interior incl. the staircase) dropped WHILE THE
GAZE LOOKED STRAIGHT AT IT - "stairs disappear and you can walk on
them", and the roof/edge flap as the gaze swung the marginal admissions.
Vertical doorways were immune (the lift slides their planes along
themselves) - exactly why this hit stairs/decks/floors and not doors.

Chase chain (the apparatus did all the work): [viewer] print-on-change
probe with eye@mm -> the user's climb capture -> [viewer-diff] naming
the dropped cells per flip -> headless replay of the exact captured
(eye,fwd) frame: healthy UNLIFTED, reproduces ONLY with the production
lift -> gate-by-gate diagnostic (side test dot=+0.003 unlifted vs
-0.017 lifted; clip + rescue exonerated; knife-edge z-sweep all-stable,
killing the float-chaos theory).

Fix: BuildLoadedCell receives the PHYSICS (unlifted) transform; the
drawn shells keep their lift. The seal/punch fans (which read the
visibility LoadedCell's WorldTransform) now stamp TRUE depth - MORE
consistent with the unlifted terrain they protect.

Pins: CapturedTopOfStairs_MainCellStaysInFlood - arm 1 (unlifted =
post-fix production) asserts the main cell admitted at the captured
frame; arm 2 (lifted) is the mechanism canary asserting the drop, with
instructions if it ever starts passing. Plus the gate-by-gate
diagnostic + knife-edge sweep as the investigation record.

Also this session: Issue127FloodFlipReplayTests (the captured 4 cm
outdoor flip pair replays STABLE across fovs/pre-gate arms - the
outdoor churn is NOT the flood math; remaining #127 = distant-building
admission churn, lower priority now that the tower-cell drops are
explained by the lift), and the [viewer-diff] probe (per-flip added/
removed cell naming - keep, it found this).

Suites: App 242+1skip, Core 1422+2skip, UI 420, Net 294.

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

tests/AcDream.App.Tests/Rendering/CornerFloodReplayTests.cs

@@ -56,6 +56,11 @@ public class CornerFloodReplayTests
     /// cell-local space, local AABB, world transform from EnvCell.Position.
     /// </summary>
     internal static LoadedCell LoadCell(DatCollection dats, uint cellId)
+        => LoadCell(dats, cellId, Vector3.Zero);
+
+    /// <summary>worldOffset: block offset for multi-landblock fixtures (dat cell
+    /// positions are landblock-local; a neighbour block needs ±192 per axis).</summary>
+    internal static LoadedCell LoadCell(DatCollection dats, uint cellId, Vector3 worldOffset)
     {
         var envCell = dats.Get<DatEnvCell>(cellId)
             ?? throw new InvalidOperationException($"EnvCell 0x{cellId:X8} not found");
@@ -66,7 +71,7 @@ public class CornerFloodReplayTests
 
         var cellTransform =
             Matrix4x4.CreateFromQuaternion(envCell.Position.Orientation) *
-            Matrix4x4.CreateTranslation(envCell.Position.Origin);
+            Matrix4x4.CreateTranslation(envCell.Position.Origin + worldOffset);
         Matrix4x4.Invert(cellTransform, out var inverse);
 
         var boundsMin = new Vector3(float.MaxValue);
@@ -139,7 +144,7 @@ public class CornerFloodReplayTests
         return new LoadedCell
         {
             CellId = cellId,
-            WorldPosition = envCell.Position.Origin,
+            WorldPosition = envCell.Position.Origin + worldOffset,
             WorldTransform = cellTransform,
             InverseWorldTransform = inverse,
             LocalBoundsMin = boundsMin,