#119-residual: tower-ascent harness pins the roof-lip flood gap; barrel claim RETRACTED (user axiom: not in retail)

User verdict on the post-#120 build: "Barrel is gone and more stairs
exist" - the #120 fix partially cured the tower, and the earlier
"legit dat barrels on the landings" claim is RETRACTED (USER AXIOM: the
barrel is NOT in the tower in retail; what the user saw was itself a
render artifact of the corrupted floods, and what the 0x020005D8 cell
statics actually render as is unverified - do not assume barrel).

Remaining tower bugs, both PINNED by TowerAscentReplayTests (the #118
exit-walk pattern, vertical - a helix ascent with the gaze locked ON
the staircase, so a cull has no gaze excuse):
- steps 195-201 (eye z 126.9-127.3, the roof-lip band between the main
  cell's ceiling at 126.8 and the roof aperture plane at ~127.2) resolve
  OUTDOOR and the per-building exterior flood admits NOTHING (flood=1 =
  the outdoor node alone): the eye is above every side aperture's useful
  view and ON/INSIDE the roof aperture's plane, so BuildFromExterior's
  seed side-test / in-plane reject refuses every exit portal. The tower
  interior never floods -> the staircase (a 0x0107 static) cone-culls
  while staying walkable (user symptom 1), and the roof-lip cell
  geometry flaps as the live eye bobs across the band's edges (user
  symptom 2). One mechanism, both symptoms.
- The pin is committed as a SKIPPED red test
  (TowerAscent_StaircaseStaysConeVisible_EveryStep; the skip reason
  carries the defect) so the suite stays green - un-skip with the fix.
- TowerAscent_RootDoesNotPingPong + the per-step diagnostic stay active.

Fix direction (oracle-first, next): determine which side diverges from
retail - (a) viewer-cell resolution (retail curr_cell may keep the eye
INTERIOR through the band: keep-curr above open-top cells / cell BSP
classifying the parapet bowl as inside 0x010A, where our resolution
demotes to outdoor), or (b) exterior seed admission (retail
ConstructView(CBldPortal) Sidedness with an in-plane eye). Grep the
named decomp for both before touching either layer.

Suites: App 238 + 1 skip (236+3 new, 1 pinned), Core 1419+2skip,
UI 420, Net 294.

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

tests/AcDream.App.Tests/Rendering/Issue120ReciprocalPingPongTests.cs

@@ -39,7 +39,7 @@ public class Issue120ReciprocalPingPongTests
     private readonly ITestOutputHelper _out;
     public Issue120ReciprocalPingPongTests(ITestOutputHelper output) => _out = output;
 
-    private static Dictionary<uint, LoadedCell> LoadAllInteriorCells(DatCollection dats, uint landblock)
+    internal static Dictionary<uint, LoadedCell> LoadAllInteriorCells(DatCollection dats, uint landblock)
     {
         var lbi = dats.Get<DatLandBlockInfo>(landblock | 0xFFFEu);
         Assert.NotNull(lbi);