feat(lighting): A7 visible-cell light scoping + [indoor-light] probe (NOT the #176/#177 fix)

Port retail's per-frame light collection: the point-light pool is built from ONLY the
currently-visible cells' lights, matching CObjCell::add_*_to_global_lights
(0x0052b350/0x0052b390) walked over CEnvCell::visible_cell_table (0x0052d410) — not a
flat world-space set capped at 128-nearest-camera.

- LightSource.CellId (retail insert_light arg6 -> RenderLight +0x6c); tagged at both
  registration sites from entity.ParentCellId (live weenie fixtures + dat EnvCell statics).
- LightManager.BuildPointLightSnapshot(camPos, visibleCells): a light joins the pool iff
  CellId==0 (viewer/global) or its cell is in the flood. 128 cap kept as a now-non-biting
  backstop (retail's is 40 static + 7 dynamic, 0x0081ec94/8).
- Threaded via RetailPViewDrawContext.RebuildScopedLights, invoked in DrawInside after the
  flood resolves prepareCells and before the draws (renderers select from the same
  in-place-rebuilt PointSnapshot; EnvCellRenderer clears its per-cell cache each pass).
- [indoor-light] probe (ACDREAM_PROBE_INDOOR_LIGHT=1) dumps the scoped-pool SET COMPOSITION.
  Un-skips LightManagerTests.PointSnapshot_HubScaleLightCount_ObjectSelectionIsCameraInvariant.

CORRECTION: the handoff called the camera-cap the "confirmed" #176/#177 mechanism. The probe
PROVES scoping works (291 Hub fixtures -> pool of 1-9, ~285 through-floor lights dropped/frame,
CellIds match the flood), but the user's VISUAL GATE showed BOTH symptoms unchanged. So pool
composition is NOT the cause. #176 real cause = an over-bright purple point light
(intensity=100, color 0.784,0,0.784 -- from [light-detail]); #177 = a portal-visibility miss
(stairs not drawn looking back). Both stay OPEN. This change is retail-faithful and retires the
camera-eviction latent bug; kept as such, not as the symptom fix. Register AP-85 corrected;
ISSUES #176/#177 re-diagnosed; render digest banner updated.

Decomp: insert_light 0x0054d1b0, minimize_object_lighting 0x0054d480, calc_point_light
0x0059c8b0; pseudocode docs/research/2026-07-06-a7-per-cell-lighting-pseudocode.md.
Suites green: Core 2595 + 2 skip, App 719 + 2 skip.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/AcDream.Core/Lighting/LightSource.cs

@@ -46,6 +46,12 @@ public sealed class LightSource
     public float     Range = 10f;     // metres, hard cutoff
     public float     ConeAngle = 0f;  // radians, Spot only
     public uint      OwnerId;         // attached entity id; 0 = world-global
+    public uint      CellId;          // owning cell id (0xLLLLNNNN); 0 = cell-less/global (viewer fill, sun).
+                                      // Retail carries this on the RenderLight (insert_light arg6, +0x6c) so the
+                                      // per-frame pool can be built from only the VISIBLE cells' lights
+                                      // (CObjCell::add_*_to_global_lights over CEnvCell::visible_cell_table).
+                                      // acdream uses it to scope BuildPointLightSnapshot — a cell-tagged light is
+                                      // only a candidate when its cell is visibly flooded (#176/#177 A7 fix).
     public bool      IsLit = true;    // SetLightHook latch
     public bool      IsDynamic;       // #143: true = D3D hardware path (1/d att, range×1.5);
                                       // false = static dat-baked bake (1/d³, range×1.3)