docs(overhaul): correct S5 c1 review comments

Remove the deleted outdoor-fallback claim, describe the visible-cell union as diagnostics rather than a shared admission answer, and distinguish the landscape particle, resident-light, and future shadow consumers.

Correct ParticleSystem complexity prose: only the SortedSet indexes have logarithmic lifecycle edges; the view list uses binary-search insertion with linear shift and linear removal.

Focused verification: Core ParticleSystemTests 47/47; App visibility/terrain/frame/renderer 38/38; AP-116 settings/live-object 3/3; git diff --check clean. No behavior, tests, register, or architecture change.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/AcDream.App/Rendering/Vfx/ParticleVisibilityController.cs

@@ -41,10 +41,11 @@ public sealed class ParticleVisibilityController : IWorldSceneParticleVisibility
     }
 
     /// <summary>
-    /// Declares that this frame has an authoritative world-visibility product.
-    /// That product can come from the unified retail PView or from the outdoor
-    /// landscape fallback. Login and portal-space frames deliberately omit it;
-    /// dedicated pass and examination emitters carry explicit bypass policies.
+    /// Declares that this frame has the completed retail PView product: one
+    /// viewer position plus its exact walk-owned landscape-cell set. Frames
+    /// without that PView product, including login, portal space, and the
+    /// null-root terrain safety draw, deliberately omit it; dedicated-pass and
+    /// examination emitters carry explicit bypass policies.
     /// </summary>
     public void UseWorldView()
     {

src/AcDream.App/Rendering/Walk/WalkFrameDriver.cs

@@ -868,11 +868,14 @@ internal sealed class WalkFrameDriver : IWalkEventSink, IWalkLookInViewSource
     }
 
     /// <summary>
-    /// Copies the walk's complete retail <c>CObjCell::IsInView</c> answer:
-    /// EnvCells reached by interior floods/look-ins plus outdoor land cells
-    /// visited by the landscape walk. The two families stay separately
-    /// retained because only the first is valid EnvCell batch input, but
-    /// particles, lights, and shadows consume their union.
+    /// Copies the walk's diagnostic union: EnvCells reached by interior
+    /// floods/look-ins plus outdoor land cells visited by the landscape walk.
+    /// The two families remain separately retained because EnvCells are shell
+    /// preparation input while only the landscape half feeds land-cell particle
+    /// eligibility; EnvCell particle eligibility is the constant-true virtual.
+    /// Point lights use the resident registry, and directional-shadow use of the
+    /// landscape product remains owned by S5-c2. No admission path consumes this
+    /// union as a complete <c>CObjCell::IsInView</c> answer.
     /// </summary>
     internal void CopyVisibleCellsTo(HashSet<uint> destination)
     {

src/AcDream.Core/Vfx/ParticleSystem.cs

@@ -14,16 +14,17 @@ public sealed class ParticleSystem : IParticleSystem
     private readonly EmitterDescRegistry _registry;
     private readonly Random _rng;
     private readonly Dictionary<int, ParticleEmitter> _byHandle = new();
-    // Handles are monotonic, so sorted indexes preserve retail emitter-spawn
-    // order while making every lifecycle edge O(log E). The old List.Remove
-    // hard-stop path was O(E) and became visible when portal routes retained
-    // thousands of finite/fading emitters.
+    // Handles are monotonic, so the SortedSet indexes preserve retail
+    // emitter-spawn order while making their lifecycle edges O(log E). Their
+    // predecessor List.Remove hard-stop path was O(E) and became visible when
+    // portal routes retained thousands of finite/fading emitters.
     private readonly SortedSet<int> _allHandles = [];
     private readonly SortedSet<int> _simulationHandles = [];
     // ApplyRetailView is a per-frame production path. SortedSet's enumerator
-    // allocates its traversal stack, so retain this subset as a sorted list;
-    // lifecycle mutations pay the binary insertion/removal cost and the
-    // warmed view walk stays allocation-free in emitter-spawn order.
+    // allocates its traversal stack, so retain this subset as a sorted list.
+    // Insertion uses a binary search followed by a linear list shift; removal
+    // searches and compacts linearly. Lifecycle mutations pay those costs so
+    // the warmed view walk stays allocation-free in emitter-spawn order.
     private readonly List<int> _worldSimulationHandles = [];
     private readonly SortedSet<int>[] _renderableHandlesByPass =
         [[], [], []];