T6 (BR-7) C4: straddle-only outside-add (A6.P5 widening DELETED) + #90 stickiness removed

The two remaining flagged workarounds retired, per the BR-7 plan +
the WF1 [MEDIUM] correction (re-gate, do NOT delete the outside-add):

1. A6.P5 hasExitPortal topology widening DELETED. Outdoor cells enter the
   collision cell array ONLY on the retail straddle gate - |dist| <
   radius + F_EPSILON against an exterior portal plane
   (CEnvCell::find_transit_cells Ghidra 0x0052c820, gate 0052c9d6,
   live-binary verified) - the same flag that already gated the
   membership pick (#112 rider). The widening existed so outdoor-
   registered doors stayed findable from indoor cells under the old flat
   registry query; with per-cell shadow lists the door is found in the
   straddle-admitted outdoor cell's own list (tick-13558 pin holds).
   The hasExitPortal out-param + plumbing deleted from
   FindTransitCellsSphere; the AddAllOutsideCells call in
   BuildCellSetAndPickContaining re-gated on exitOutsideStraddle
   (once-per-walk = retail CELLARRAY.added_outside).

2. #90 ResolveCellId sphere-overlap stickiness REMOVED (the 4ca3596
   workaround, deferred-to-A6.P4 in the physics digest). It was dead
   code: the method's only caller is FindEnvCollisions' cache-null TEST
   fallback, and the indoor branch (where the stickiness lived) required
   a non-null DataCache. Production membership flows exclusively through
   the collide-then-pick advance whose ordered-array hysteresis (current
   cell at index 0, interior-wins-break) is the retail mechanism the
   workaround approximated. ResolveCellId reduced to the bare
   prefix-preserving outdoor re-derive, documented test-only.

Test updates (pins of the deleted behaviors inverted to retail):
- A6P5_BuildCellSetFromIndoorStart_ReachesDoorOutdoorCell (asserted the
  topology widening verbatim) -> DeepInteriorSphere_NoStraddle_
  AddsNoOutdoorCells: a deep-interior sphere admits NO outdoor cells.
- A6P5_BuildCellSetFromAlcove... -> AlcoveSphere_StraddlesExitPortal_
  ReachesDoorOutdoorCell (the captured alcove position genuinely
  straddles - the retail-positive half).
- Issue112MembershipTests straddle pin + the second-sphere straddle test
  updated to the single-flag signature.

Suites: Core 1416/0/2, App 225, UI 420, Net 294 - green.

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

tests/AcDream.Core.Tests/Physics/CellTransitFindTransitCellsSphereTests.cs

@@ -212,7 +212,7 @@ public class CellTransitFindTransitCellsSphereTests
 
         CellTransit.FindTransitCellsSphere(
             cache, exitCell, currentCellId: 0xA9B40100u,
-            spheres, spheres.Length, candidates, out bool exitOutside, out _);
+            spheres, spheres.Length, candidates, out bool exitOutside);
 
         Assert.True(exitOutside);
     }