fix(physics): #91 — query indoor cell shadows in FindObjCollisions

Interior items (fireplaces, tables, chests) registered via A1.5's
ShadowObjectRegistry.Register `cellScope` parameter (commit 4d3bf6f)
are stored under their ParentCellId key (e.g. 0xA9B40121). But
GetNearbyObjects's broad-phase only iterates outdoor 24m landcell
keys (0xA9B40029 etc) and never looks up indoor cell keys, so
interior shadows were registered but unreachable. User-visible
symptom: tables/boxes/fireplaces don't block movement, while walls
DO block (the indoor BSP path is separate).

Fix: GetNearbyObjects accepts an optional indoorCellIds parameter
and additionally queries _cells[indoorCellId] for each entry with
low-byte >= 0x0100u. FindObjCollisions computes the set via
CellTransit.FindCellSet (same set A4 uses for multi-cell BSP
iteration) and passes it through. Outdoor seeds typically produce
sets containing only outdoor land-cells which the new branch filters
out, so the outdoor-only behavior is preserved.

1147 + 8 baseline maintained. Closes the user-reported regression
"walls block now correct but interior items such as tables and boxes
or fireplaces do not block."

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.Core/Physics/ShadowObjectRegistry.cs

@@ -242,14 +242,43 @@ public sealed class ShadowObjectRegistry
     /// Get all objects near a world position. Searches the given landblock plus
     /// all 8 adjacent landblocks to handle objects near cell/landblock boundaries.
     /// Within each landblock, queries only the cells the query sphere overlaps.
+    ///
+    /// <para>
+    /// Issue #91 (2026-05-20): the optional <paramref name="indoorCellIds"/>
+    /// parameter is the candidate set of indoor cells the foot-sphere overlaps
+    /// (from <see cref="CellTransit.FindCellSet"/>). When supplied, indoor
+    /// shadows registered via <see cref="Register"/>'s <c>cellScope</c>
+    /// parameter (A1.5 fix at `4d3bf6f`) are ALSO included in the result.
+    /// Without this, interior statics (fireplaces, tables, chests) registered
+    /// against e.g. `0xA9B40121` are stored under that key but the outdoor-
+    /// grid lookup (cell ids like `0xA9B40029`) never queries the indoor key.
+    /// Net effect pre-fix: interior items don't block movement.
+    /// </para>
     /// </summary>
     public void GetNearbyObjects(Vector3 worldPos, float queryRadius,
                                   float worldOffsetX, float worldOffsetY, uint landblockId,
-                                  List<ShadowEntry> results)
+                                  List<ShadowEntry> results,
+                                  System.Collections.Generic.IReadOnlyCollection<uint>? indoorCellIds = null)
     {
         results.Clear();
         var seen = new HashSet<uint>();
 
+        // Indoor-scoped shadows (A1.5 cellScope). Query first so the
+        // outdoor-grid lookup below skips duplicates via `seen`.
+        if (indoorCellIds is not null)
+        {
+            foreach (uint indoorCellId in indoorCellIds)
+            {
+                if ((indoorCellId & 0xFFFFu) < 0x0100u) continue;  // skip outdoor ids
+                if (!_cells.TryGetValue(indoorCellId, out var list)) continue;
+                foreach (var entry in list)
+                {
+                    if (seen.Add(entry.EntityId))
+                        results.Add(entry);
+                }
+            }
+        }
+
         // Extract landblock X/Y from the ID.
         int lbX = (int)((landblockId >> 24) & 0xFF);
         int lbY = (int)((landblockId >> 16) & 0xFF);

src/AcDream.Core/Physics/TransitionTypes.cs

@@ -1911,10 +1911,29 @@ public sealed class Transition
         // iteration. Allocate per call (cheap — typically 0-5 entries).
         var nearbyObjs = new List<ShadowEntry>();
         float queryRadius = sphereRadius + movement.Length() + 5f;
+
+        // Issue #91 (2026-05-20): interior items (fireplaces, tables, chests)
+        // are registered with `cellScope = ParentCellId` per A1.5's fix at
+        // `4d3bf6f`. They're stored under the indoor cell key (e.g.
+        // `0xA9B40121`), but GetNearbyObjects's outdoor-grid lookup (cells
+        // like `0xA9B40029`) never queries that key. Compute the indoor
+        // candidate set via CellTransit.FindCellSet — same set A4 uses for
+        // multi-cell BSP iteration — and pass it through so indoor shadows
+        // are also picked up. When the seed is outdoor the set typically
+        // contains only outdoor land-cells which the new branch in
+        // GetNearbyObjects skips via the `< 0x0100u` filter, so behavior
+        // matches the prior outdoor-only path.
+        // (engine.DataCache is non-null per the early-return at top of
+        // FindObjCollisions; redundant inner check would confuse nullable
+        // flow analysis.)
+        _ = CellTransit.FindCellSet(engine.DataCache, currPos, sphereRadius,
+                                    sp.CheckCellId, out var indoorCellIds);
+
         engine.ShadowObjects.GetNearbyObjects(
             currPos, queryRadius,
             worldOffsetX, worldOffsetY, landblockId,
-            nearbyObjs);
+            nearbyObjs,
+            indoorCellIds);
 
         foreach (var obj in nearbyObjs)
         {