feat(A7.L1): scope the point-light pool by last frame's visible cells (#79/#93/#176/#177)

The Town Network hub (498 registered fixtures) starved the player's own
room: BuildPointLightSnapshot's player-nearest-128 cap sorts by raw
Euclidean distance, which isn't a reliable proxy for "same room" in a
dense maze — a fixture on the other side of a wall can be geometrically
closer than the room's own torches and win the cap. LightSource.CellId
tagging and the [indoor-light] membership probe already existed from the
c500912b/#176 arc; the missing piece was a candidacy filter.

BuildPointLightSnapshot(playerWorldPos, visibleCells) now narrows
candidates to the frame's actual visible cells before the existing
dynamics-first player-nearest cap runs (cell-less lights, e.g. the viewer
fill, always included). GameWindow feeds LAST FRAME's already-rendered
RetailPViewFrameResult.DrawableCells — one frame of latency instead of
re-threading a mid-DrawInside callback, which was the exact mechanism
(c500912b) that caused the earlier #176 seam-floor flicker regression.
The distance-sort anchor stays the player, unchanged.

AP-85 updated in place (third revision) rather than adding a new row —
same underlying divergence, now with the render-visibility approximation
of retail's true DBObj-load/flush-bounded resident registry documented
alongside its residual risk (one unscoped frame on portal re-entry).

Core 2652+2skip / App 741+2skip / UI 425 / Net 385 green. Pending: user
visual gate at the Town Network fountain, and a #176 corridor-seam
non-regression recheck (Facility Hub, different landblock).

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

src/AcDream.Core/Rendering/RenderingDiagnostics.cs

@@ -282,13 +282,20 @@ public static class RenderingDiagnostics
     /// [indoor-light] pool=<M> cellLess=<K> registered=<R> capped=<R-M>
     ///                byCell=[0x<id>:<count>,...]
     /// </code>
-    /// #176 correction (2026-07-06, same day): the pool is now retail's
-    /// RESIDENT-cell collection capped nearest-the-PLAYER — visible-cell scoping
-    /// (the gaze-coupled pool) was the #176 flicker mechanism and is deleted, so
-    /// the line no longer carries <c>visibleCells/droppedNonVisible</c>. The
-    /// diagnostic value that remains: <c>cellLess==pool</c> in a fixture-rich room
-    /// still means cell tagging FAILED (ParentCellId not flowing), and
-    /// <c>byCell</c> shows which cells' lights are pooled.
+    /// #176 correction (2026-07-06): the pool became retail's RESIDENT-cell
+    /// collection capped nearest-the-PLAYER — the earlier gaze-coupled scoping
+    /// (rebuilding the pool from a freshly re-flooded CAMERA-seeded set,
+    /// <c>c500912b</c>) was the #176 flicker mechanism and was deleted.
+    /// A7.L1 (2026-07-09): visible-cell scoping is BACK, but sourced differently —
+    /// <c>LightManager.BuildPointLightSnapshot</c> now takes an optional
+    /// <c>visibleCells</c> filter that <c>GameWindow</c> feeds from LAST FRAME's
+    /// already-rendered <c>RetailPViewFrameResult.DrawableCells</c> (one frame of
+    /// latency, no independent re-flood, no callback threaded into DrawInside) —
+    /// fixes the Town Network starvation case (463 fixtures, a wall-adjacent
+    /// corridor's fixtures out-ranking the player's own room in raw Euclidean
+    /// distance) without reproducing the #176 mechanism. <c>byCell</c> shows which
+    /// cells' lights are pooled; <c>cellLess==pool</c> in a fixture-rich room still
+    /// means cell tagging FAILED (ParentCellId not flowing).
     /// Output-only, inert when off. Initial state from <c>ACDREAM_PROBE_INDOOR_LIGHT=1</c>.
     /// </summary>
     public static bool ProbeIndoorLightEnabled { get; set; } =
@@ -576,8 +583,8 @@ public static class RenderingDiagnostics
     /// point-light pool: the SET COMPOSITION the <c>[light]</c> counts can't show.
     /// Cheap no-op when <see cref="ProbeIndoorLightEnabled"/> is false; otherwise
     /// fires at most once per second. Called from
-    /// <c>LightManager.BuildPointLightSnapshot</c> (the resident collection —
-    /// #176 correction removed the visible-cell scoping).
+    /// <c>LightManager.BuildPointLightSnapshot</c> — <paramref name="scopedSnapshot"/>
+    /// already reflects any last-frame visible-cell scoping (A7.L1, 2026-07-09).
     /// </summary>
     /// <param name="allRegistered">Every registered light (<c>LightManager._all</c>).</param>
     /// <param name="scopedSnapshot">The point-light pool just built.</param>