feat(physics): Phase 2 — wire CellBSP + Portals into CellPhysics

Adds PortalInfo struct and extends CellPhysics with CellBSP (third BSP
for point-in-cell tests, typed CellBSPTree from DatReaderWriter),
Portals (from envCell.CellPortals), PortalPolygons (resolved
cellStruct.Polygons — portals reference visible polys, not
PhysicsPolygons), and VisibleCellIds (populated for future use;
envCell.VisibleCells is List<UInt16>, not Dictionary).

Deletes CellPhysics.LocalAabbMin/Max and PhysicsDataCache.TryFindContainingCell
— Phase D's AABB shortcut is gone. CacheCellStruct's AABB compute
removed; the [cell-cache] diagnostic updated with portal/visible counts
instead.

CacheCellStruct signature gains an EnvCell parameter (one call site in
GameWindow.cs:5384 updated). ResolveOutdoorCellId drops the
TryFindContainingCell call; portal-graph CellTransit replaces it next.

ResolveOutdoorCellIdTests object initializers had the deleted AABB
properties stripped temporarily so the build stays green; the file gets
replaced wholesale in the next commit (CellTransit integration). Those
2 AABB-containment tests continue to fail (they were pre-broken on this
branch); no new failures introduced.

Spec: docs/superpowers/specs/2026-05-19-indoor-portal-cell-tracking-design.md
Plan: docs/superpowers/plans/2026-05-19-indoor-portal-cell-tracking.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -0,0 +1,67 @@
+using System.Numerics;
+using AcDream.Core.Physics;
+using Xunit;
+
+namespace AcDream.Core.Tests.Physics;
+
+public class CellPhysicsPortalWiringTests
+{
+    [Fact]
+    public void NewFields_HaveSensibleDefaults()
+    {
+        var cp = new CellPhysics
+        {
+            WorldTransform = Matrix4x4.Identity,
+            InverseWorldTransform = Matrix4x4.Identity,
+            Resolved = new System.Collections.Generic.Dictionary<ushort, ResolvedPolygon>(),
+        };
+
+        Assert.Null(cp.CellBSP);
+        Assert.Empty(cp.Portals);
+        Assert.Null(cp.PortalPolygons);
+        Assert.Empty(cp.VisibleCellIds);
+    }
+
+    [Fact]
+    public void NewFields_AcceptInitValues()
+    {
+        var portal = new PortalInfo(otherCellId: 0x0101, polygonId: 5, flags: 0);
+
+        var cp = new CellPhysics
+        {
+            WorldTransform = Matrix4x4.Identity,
+            InverseWorldTransform = Matrix4x4.Identity,
+            Resolved = new System.Collections.Generic.Dictionary<ushort, ResolvedPolygon>(),
+            Portals = new[] { portal },
+            VisibleCellIds = new System.Collections.Generic.HashSet<uint> { 0xA9B40101 },
+        };
+
+        Assert.Single(cp.Portals);
+        Assert.Equal((ushort)0x0101, cp.Portals[0].OtherCellId);
+        Assert.Contains(0xA9B40101u, cp.VisibleCellIds);
+    }
+
+    [Fact]
+    public void CellPhysics_PortalsRoundTrip()
+    {
+        var portals = new[]
+        {
+            new PortalInfo(otherCellId: 0x0101, polygonId: 7, flags: 0),
+            new PortalInfo(otherCellId: 0xFFFF, polygonId: 8, flags: 2),
+        };
+
+        var cp = new CellPhysics
+        {
+            WorldTransform = Matrix4x4.Identity,
+            InverseWorldTransform = Matrix4x4.Identity,
+            Resolved = new System.Collections.Generic.Dictionary<ushort, ResolvedPolygon>(),
+            Portals = portals,
+        };
+
+        Assert.Equal(2, cp.Portals.Count);
+        Assert.Equal((ushort)0x0101, cp.Portals[0].OtherCellId);
+        Assert.True(cp.Portals[0].PortalSide);
+        Assert.Equal((ushort)0xFFFF, cp.Portals[1].OtherCellId);
+        Assert.False(cp.Portals[1].PortalSide);
+    }
+}

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

@@ -0,0 +1,35 @@
+using AcDream.Core.Physics;
+using Xunit;
+
+namespace AcDream.Core.Tests.Physics;
+
+public class PortalInfoTests
+{
+    [Fact]
+    public void PortalSide_FlagsBit2Clear_ReturnsTrue()
+    {
+        var portal = new PortalInfo(otherCellId: 0x0101, polygonId: 5, flags: 0);
+        Assert.True(portal.PortalSide);
+    }
+
+    [Fact]
+    public void PortalSide_FlagsBit2Set_ReturnsFalse()
+    {
+        var portal = new PortalInfo(otherCellId: 0x0101, polygonId: 5, flags: 2);
+        Assert.False(portal.PortalSide);
+    }
+
+    [Fact]
+    public void PortalSide_OtherBitsSet_FollowsOnlyBit2()
+    {
+        var portal = new PortalInfo(otherCellId: 0x0101, polygonId: 5, flags: 0xFF & ~2);
+        Assert.True(portal.PortalSide);
+    }
+
+    [Fact]
+    public void OtherCellId_StoredAsLowSixteenBits()
+    {
+        var portal = new PortalInfo(otherCellId: 0xFFFF, polygonId: 5, flags: 0);
+        Assert.Equal((ushort)0xFFFF, portal.OtherCellId);
+    }
+}

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

@@ -46,8 +46,6 @@ public class ResolveOutdoorCellIdIndoorContainmentTests
             Resolved = new Dictionary<ushort, ResolvedPolygon> { [0] = poly },
             WorldTransform = world,
             InverseWorldTransform = inv,
-            LocalAabbMin = min,
-            LocalAabbMax = max,
         };
     }
 
@@ -121,8 +119,6 @@ public class ResolveOutdoorCellIdIndoorContainmentTests
             Resolved = new Dictionary<ushort, ResolvedPolygon> { [0] = poly },
             WorldTransform = rotation,
             InverseWorldTransform = inv,
-            LocalAabbMin = -halfExtent,
-            LocalAabbMax =  halfExtent,
         };
 
         var engine = new PhysicsEngine();