fix(streaming): recover the player from the pending bucket — invisible-player / world-not-loading bug

Root cause (confirmed live via ACDREAM_PROBE_ENT): a persistent server-spawned
entity that spawns into a not-yet-loaded landblock is parked in
GpuWorldState._pendingByLandblock. RelocateEntity — called every frame to keep
the player homed to its current landblock so it draws — scanned ONLY _loaded, so
it silently no-op'd on a pending entity. The player then fell through ALL of the
recovery paths: the AddLandblock pending-drain had already run (empty) before the
cold-spawn churn re-parked the player; the server-object re-hydrate excludes the
player by design ("persistent-rescue owns it"); and RelocateEntity couldn't reach
a pending entity. Net: the player stayed stranded in pending, hidden forever.

Probe evidence (cold-spawn at 0xADAF): `[ent] APPEND guid=0x5000000A
lb=0xADAFFFFF -> PENDING(hidden)`, no later `DRAWSET PRESENT` — while the sibling
NPCs `re-hydrated 3 server object(s) into landblock 0xADAFFFFF` and drew fine.

This is the mechanism behind BOTH reported symptoms: cold-spawn "everything gone
/ invisible" AND "character disappears running out of Holtburg far enough" — both
are "player parked in pending, never recovered" (run-out crosses into a
still-streaming landblock; cold-spawn spawns into one).

Fix: RelocateEntity now removes the entity from whichever bucket it occupies
(_loaded OR _pendingByLandblock) via RemoveEntityFromAllBuckets, then re-appends
to its current landblock — promoting a stranded pending entity to drawn as soon
as its landblock is loaded. Keeps the fast-path early-return for a settled
entity (no per-frame churn).

NOT R5-V2: verified line-by-line that the voyeur/target wiring is read-only w.r.t.
position/cell/landblock/streaming — this is a pre-existing streaming bug. The
separate cold-spawn `cells=0` (outdoor spawn placed before Near-tier cells load,
no re-snap) is benign for outdoor placement (terrain-Z is used) and filed
separately; it does not block visibility, which this fix restores.

Test: GpuWorldStateTests.RelocateEntity_StrandedInPending_MovesToLoadedTarget
(red before, green after). Full suite 4007 green.

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

src/AcDream.App/Streaming/GpuWorldState.cs

@@ -255,7 +255,43 @@ public sealed class GpuWorldState
     {
         if (entity.ServerGuid == 0) return;
 
-        // Remove from current landblock (find it by scanning)
+        uint canonical = (newCanonicalLb & 0xFFFF0000u) | 0xFFFFu;
+
+        // Fast path: already drawn in the correct loaded bucket → nothing to do
+        // (avoids per-frame list churn for a settled, stationary entity).
+        if (_loaded.TryGetValue(canonical, out var target))
+        {
+            foreach (var e in target.Entities)
+                if (ReferenceEquals(e, entity)) return;
+        }
+
+        // Remove the entity from wherever it currently lives — a loaded bucket
+        // OR a pending bucket — then re-append to its current landblock.
+        //
+        // Scanning _pendingByLandblock is the 2026-07-03 fix for the cold-spawn /
+        // run-out "invisible player" bug: a persistent (server-spawned) entity
+        // that spawned into a not-yet-loaded landblock sits in _pendingByLandblock,
+        // and the old code scanned ONLY _loaded — so it silently no-op'd and left
+        // the player stranded, hidden, even after its landblock finished loading
+        // (the AddLandblock pending-drain had already run empty before the churn
+        // re-parked the player, and the player is excluded from the server-object
+        // re-hydrate — so RelocateEntity was the ONLY path that could recover it,
+        // and it couldn't reach a pending entity). Re-appending routes the entity
+        // to _loaded (drawn) when its landblock is loaded, or back to pending to
+        // await AddLandblock otherwise.
+        RemoveEntityFromAllBuckets(entity);
+        AppendLiveEntity(canonical, entity);
+    }
+
+    /// <summary>
+    /// Remove <paramref name="entity"/> (by reference) from whichever
+    /// <see cref="_loaded"/> or <see cref="_pendingByLandblock"/> bucket it
+    /// currently occupies. At most one bucket holds a given entity, so this
+    /// stops after the first hit. Called by <see cref="RelocateEntity"/> before
+    /// re-appending, so a stranded pending entity can be promoted.
+    /// </summary>
+    private void RemoveEntityFromAllBuckets(WorldEntity entity)
+    {
         foreach (var kvp in _loaded)
         {
             var entities = kvp.Value.Entities;
@@ -263,23 +299,21 @@ public sealed class GpuWorldState
             {
                 if (ReferenceEquals(entities[i], entity))
                 {
-                    if (kvp.Key == newCanonicalLb) return; // already in the right place
-
-                    // Remove from old
                     var newList = new List<WorldEntity>(entities.Count - 1);
                     for (int j = 0; j < entities.Count; j++)
                         if (j != i) newList.Add(entities[j]);
                     _loaded[kvp.Key] = new LoadedLandblock(
-                        kvp.Value.LandblockId,
-                        kvp.Value.Heightmap,
-                        newList);
-
-                    // Add to new (via AppendLiveEntity which handles pending)
-                    AppendLiveEntity(newCanonicalLb, entity);
+                        kvp.Value.LandblockId, kvp.Value.Heightmap, newList);
                     return;
                 }
             }
         }
+
+        foreach (var kvp in _pendingByLandblock)
+        {
+            if (kvp.Value.Remove(entity))
+                return;
+        }
     }
 
     public void RemoveLandblock(uint landblockId)