feat(render) Campaign FW1: look-in adjudication - the GetVisible load gate

The per-building join diagnostic PASSES (001a/0022 portal tables lead
exactly to the traced a9b4016x punch cells; every BSP PortalRef indexes
validly), and the eight-arm gate-decode sweep proves NO plane-sign x
side-flag combination reproduces retail. Together they pin the missing
mechanism: CEnvCell::GetVisible gates punches by the LOADED interior
cell set around the player - retail punched only the two buildings
nearest the player cell; the replay loads every interior so geometry
alone over-punches. Next port piece: the interior load radius (the
landcell stab-list pull). Both diagnostics stay in the suite (the sweep
Skip-parked with the verdict).

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

tests/AcDream.App.Tests/Rendering/Walk/WalkLookInGateSweepTests.cs

@@ -0,0 +1,115 @@
+using AcDream.App.Tests.Rendering;
+using AcDream.App.Rendering.Walk;
+using DatReaderWriter;
+using DatReaderWriter.Options;
+using System.Text;
+
+namespace AcDream.App.Tests.Rendering.Walk;
+
+/// <summary>
+/// FW1 look-in gate adjudication sweep: with data joins proven correct,
+/// the wrong-building punches must come from the sidedness gate's two
+/// unvalidated inputs — the GfxObj portal-poly plane sign and the
+/// BuildingPortal side-flag decode. This sweeps all combinations against
+/// the street-outdoor fixture and reports which (if any) reproduces
+/// retail's punch set {001a, 0022}. Diagnostic: always passes; the result
+/// lands in the campaign record via the assert message when no arm matches.
+/// </summary>
+[Trait("Lane", "InstalledDat")]
+public sealed class WalkLookInGateSweepTests
+{
+    private sealed class Recorder : IWalkEventSink
+    {
+        public readonly List<WalkEvent> Events = new();
+        public void Emit(in WalkEvent walkEvent) => Events.Add(walkEvent);
+    }
+
+    [Fact(Skip = "Adjudicated 2026-08-30: NO gate decode reproduces retail, and "
+        + "the join diagnostic proves the data is right — the missing mechanism "
+        + "is CEnvCell::GetVisible's LOADED-interior-cell gate (retail punched "
+        + "only the two buildings nearest the player; their interiors were "
+        + "loaded, farther ones were not; the replay loads everything). Port "
+        + "the interior load radius (landcell stab-list pull around the "
+        + "player) and re-run this sweep to pin the plane/side decode.")]
+    public void Sweep_the_lookin_gate_decodes_against_the_street_fixture()
+    {
+        string? datDir = CornerFloodReplayTests.ResolveDatDir();
+        if (datDir is null)
+        {
+            Assert.Fail("Lane=InstalledDat requires an installed retail DAT directory.");
+        }
+        IReadOnlyList<WalkOracleFrame> frames =
+            WalkOracleTrace.Load("posed/holtburg-street-outdoor");
+        WalkOracleFrame frame = frames[1];
+        Assert.NotNull(frame.Pose);
+
+        // Retail's ground truth for this frame: which buildings punched, and
+        // which cells each punch listed.
+        string expectedPunches = PunchSignature(
+            frame.Events.Select(e => e.Kind == WalkOracleEventKind.Building
+                ? ("BLD", e.CellId!.Value, Array.Empty<uint>())
+                : e.Kind == WalkOracleEventKind.DrawCells
+                    ? ("DC", 0u, e.Cells.ToArray())
+                    : ("", 0u, Array.Empty<uint>())));
+
+        var report = new StringBuilder();
+        report.AppendLine($"RETAIL: {expectedPunches}");
+        string? winner = null;
+
+        foreach (bool flipPlanes in new[] { false, true })
+        {
+            foreach (int sideMode in new[] { 0, 1, 2, 3 })
+            {
+                // sideMode: 0 = (Flags & 0x2), 1 = inverted 0x2,
+                //           2 = (Flags & 0x1), 3 = inverted 0x1.
+                using var dats = new DatCollection(datDir!, DatAccessType.Read);
+                WalkWorldDatAdapter.FlipGfxPolygonPlanes = flipPlanes;
+                WalkWorldDatAdapter.BuildingSideMode = sideMode;
+                try
+                {
+                    WalkLandscapeDatBuilder.BuiltWorld world =
+                        WalkLandscapeDatBuilder.Build(dats, frame.Pose!.CellId);
+                    var ctx = new WalkTraceReplayContext(frame.Pose, world.Cells)
+                    {
+                        Buildings = world.Buildings,
+                    };
+                    var walk = new RetailFrameWalk();
+                    var recorder = new Recorder();
+                    walk.WalkFrame(frame.Pose.CellId, null, world.Landscape, ctx, recorder);
+                    string actual = PunchSignature(
+                        recorder.Events.Select(e => e.Kind == WalkEventKind.Building
+                            ? ("BLD", e.CellId, Array.Empty<uint>())
+                            : e.Kind == WalkEventKind.DrawCells
+                                ? ("DC", 0u, e.Cells.ToArray())
+                                : ("", 0u, Array.Empty<uint>())));
+                    string arm = $"flip={flipPlanes} side={sideMode}";
+                    report.AppendLine($"{arm}: {actual}");
+                    if (actual == expectedPunches)
+                        winner ??= arm;
+                }
+                finally
+                {
+                    WalkWorldDatAdapter.FlipGfxPolygonPlanes = false;
+                    WalkWorldDatAdapter.BuildingSideMode = 0;
+                }
+            }
+        }
+
+        Assert.True(
+            winner is not null,
+            $"no gate decode reproduces retail's punch pattern\n{report}");
+    }
+
+    private static string PunchSignature(
+        IEnumerable<(string Kind, uint Id, uint[] Cells)> events)
+    {
+        var parts = new List<string>();
+        foreach ((string kind, uint id, uint[] cells) in events)
+        {
+            if (kind == "BLD") parts.Add($"B{id:x8}");
+            else if (kind == "DC")
+                parts.Add($"D[{string.Join(',', cells.Select(c => (c & 0xFFFF).ToString("x3")))}]");
+        }
+        return string.Join("|", parts);
+    }
+}