fix(lighting): indoor interiors now lit — landblock-key bug + viewer light + weenie fixtures

The whole "indoor interiors read dark/flat vs retail" saga was ONE root-cause
bug: EnvCellRenderer.GetCellLightSet derived the landblock key as
`cellId & 0xFFFF0000` (0xXXYY0000), but landblocks are keyed by the streaming
id 0xXXYYFFFF. The lookup missed for EVERY cell, so SelectForObject never ran
and every EnvCell wall received ZERO point lights — torches, lanterns, the
viewer light, all of it. Confirmed by a [cell-light] probe: inBounds=False
selected=0 across 1M+ cell draws; after the fix inBounds=True selected=3-4.
User-confirmed the interiors now look like retail.

Three faithful additions that were blocked by the key bug (and only show now):
- Viewer light (LightManager.UpdateViewerLight): retail's SmartBox::set_viewer
  (0x00452c40) adds a white fill light at the player every frame via
  add_dynamic_light — the dominant interior fill (no sun indoors). acdream had
  NO dynamic lights at all. Params from the cdb capture: intensity 2.25,
  falloff 10, white, offset (0,0,2). Indoor-only via the AP-43 gate.
- Weenie fixture lights (OnLiveEntitySpawnedLocked): server-spawned lanterns/
  braziers carry Setup.Lights but the dat-static registration never saw
  CreateObject entities. Register on spawn; unregister on despawn
  (UnregisterOwner made unconditional). Register row AP-44.
- IndoorObjectReceivesTorches now excludes the 0xFFFF landblock marker (it is
  not an EnvCell) — fixes WbDrawDispatcherIndoorFlagTests.LandblockId_OutdoorFlag0
  (a #142 verification miss).

Divergence register: AP-44 (weenie light spawn-position, no movement tracking),
AP-47 (acdream's 128-light/camera-independent cap keeps interiors always-lit vs
retail's 40-nearest-to-player budget that pops in on approach — intentional,
user-preferred).

Investigation: docs/research/2026-06-20-indoor-torch-lantern-lighting-investigation.md

Core 1505 / App 476 green. Visual gate: user-confirmed "looks like retail now."

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.Core/Lighting/LightManager.cs

@@ -43,6 +43,7 @@ public sealed class LightManager
     private readonly List<LightSource> _all = new();
     private readonly LightSource?[] _active = new LightSource?[MaxActiveLights];
     private int _activeCount;
+    private LightSource? _viewerLight;   // retail SmartBox::viewer_light (see UpdateViewerLight)
 
     /// <summary>Current cell ambient state applied to everything.</summary>
     public CellAmbientState CurrentAmbient { get; set; }
@@ -86,6 +87,7 @@ public sealed class LightManager
         _all.Clear();
         Array.Clear(_active);
         _activeCount = 0;
+        _viewerLight = null;   // re-created + re-registered by the next UpdateViewerLight
     }
 
     /// <summary>
@@ -212,6 +214,58 @@ public sealed class LightManager
         }
     }
 
+    // ── Viewer light — retail SmartBox::set_viewer (0x00452c40) ──────────────
+    // Retail adds a white fill light pinned to the player EVERY frame via
+    // Render::add_dynamic_light. It is the dominant INTERIOR fill: the outdoor
+    // stage runs useSunlightSet(1) (sun only — dynamics are NOT enabled), but the
+    // interior stage runs minimize_envcell_lighting, which enables the dynamic
+    // lights, so EnvCell walls + indoor objects are lit by this viewer light while
+    // the player is inside. acdream registered NO dynamic lights at all, so
+    // interiors had only flat ambient and read dark/cool vs retail's lit rooms.
+    //
+    // It rides the existing point-light path: registered in _all ⇒ included in
+    // BuildPointLightSnapshot ⇒ selected by SelectForObject for nearby cells /
+    // objects. The AP-43 indoor gate (WbDrawDispatcher.IndoorObjectReceivesTorches)
+    // already restricts per-object point lights to EnvCell-parented objects, and
+    // only EnvCellRenderer selects per-cell lights, so the viewer light lights
+    // ONLY indoor draws — matching retail's interior-stage-only dynamic enable.
+    // Terrain has no point-light path, so it is unaffected.
+    //
+    // Params from the live cdb capture (reference_retail_ambient_values.md):
+    // intensity 2.25, falloff 10, colour white, offset (0,0,2) above the player
+    // (SmartBox::set_viewer player branch). Dynamic lights use rangeAdjust 1.5
+    // (config_hardware_light 0x0059ad30) ⇒ Range = 10 × 1.5 = 15 m.
+    public const float ViewerLightIntensity = 2.25f;   // GRV SmartBox.ViewerLightIntensity
+    public const float ViewerLightFalloff   = 10f;     // GRV SmartBox.ViewerLightFalloff
+    private const uint ViewerLightOwnerId   = 0xFFFFFFFFu;  // sentinel; never an entity id
+
+    /// <summary>
+    /// Reposition the always-on viewer fill light at the player (offset +2 m up),
+    /// registering it on first call. Call once per frame BEFORE
+    /// <see cref="BuildPointLightSnapshot"/> / <see cref="Tick"/>. Mirrors retail's
+    /// per-frame <c>SmartBox::set_viewer</c> add_dynamic_light; here the light lives
+    /// in <c>_all</c> and is repositioned so the existing snapshot + per-object
+    /// selection light the cell around the player. Indoor-only via the AP-43 gate
+    /// (see the note above).
+    /// </summary>
+    public void UpdateViewerLight(Vector3 playerWorldPos)
+    {
+        if (_viewerLight is null)
+        {
+            _viewerLight = new LightSource
+            {
+                Kind        = LightKind.Point,
+                ColorLinear = Vector3.One,                  // white (1,1,1)
+                Intensity   = ViewerLightIntensity,
+                Range       = ViewerLightFalloff * 1.5f,    // dynamic rangeAdjust 1.5
+                OwnerId     = ViewerLightOwnerId,
+                IsLit       = true,
+            };
+            _all.Add(_viewerLight);
+        }
+        _viewerLight.WorldPosition = playerWorldPos + new Vector3(0f, 0f, 2f);
+    }
+
     /// <summary>
     /// Select up to <see cref="MaxLightsPerObject"/> point/spot lights from
     /// <paramref name="snapshot"/> that reach the object sphere