fix(render): S3 chunk 3 re-review follow-ups

- the LandCell event doc states the deferred cross-block batch rule (the
  same-landblock lookahead text was stale);
- the AlphaSubmitMark arm's comment gives the true reason it is not a
  flush point (it only enqueues into the CPU alpha list; the drain leaves
  flush first);
- the pending terrain batch is cleared with the other transient frame
  lists in AbortFrame/BeginFrame;
- CompleteWalkTerrainFrame runs in a finally so a throwing Replay cannot
  leak its accumulated ticks into the next frame's sample;
- CopyRenderableEmittersInCell keeps its own doc comment;
- the outdoor-root LandCell pin now observes one real cell turn after its
  terrain;
- the oh1 landscape contract's stale "whole pre-stage" prose is resolved.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/AcDream.Core/Vfx/ParticleSystem.cs

@@ -606,17 +606,6 @@ public sealed class ParticleSystem : IParticleSystem
         destination.Sort(static (left, right) => left.Handle.CompareTo(right.Handle));
     }
 
-    /// <summary>
-    /// Copies the renderable emitters whose <see cref="ParticleEmitter.OwnerCellId"/>
-    /// is <paramref name="cellId"/>, retaining spawn order. Retail
-    /// <c>CPhysicsObj::add_particle_shadow_to_cell</c> (0x00514a70) gives an
-    /// emitter exactly one shadow in its own current cell, independent of its
-    /// attached owner's registry membership — a hidden/suspended owner's
-    /// emitter is still enumerated here as long as it remains renderable
-    /// (presentation-visible and view-eligible). No per-call allocation after
-    /// warmup: the bucket's own sorted handle list is copied through the
-    /// retained <see cref="_scopeHandleScratch"/> buffer.
-    /// </summary>
     /// <summary>
     /// S3 chunk 3 fix round 1 (F2): whether <paramref name="cellId"/> has any
     /// renderable emitter for <paramref name="renderPass"/>, WITHOUT copying
@@ -635,6 +624,17 @@ public sealed class ParticleSystem : IParticleSystem
             && bucket.FirstRenderableHandle != 0;
     }
 
+    /// <summary>
+    /// Copies the renderable emitters whose <see cref="ParticleEmitter.OwnerCellId"/>
+    /// is <paramref name="cellId"/>, retaining spawn order. Retail
+    /// <c>CPhysicsObj::add_particle_shadow_to_cell</c> (0x00514a70) gives an
+    /// emitter exactly one shadow in its own current cell, independent of its
+    /// attached owner's registry membership — a hidden/suspended owner's
+    /// emitter is still enumerated here as long as it remains renderable
+    /// (presentation-visible and view-eligible). No per-call allocation after
+    /// warmup: the bucket's own sorted handle list is copied through the
+    /// retained <see cref="_scopeHandleScratch"/> buffer.
+    /// </summary>
     public void CopyRenderableEmittersInCell(
         ParticleRenderPass renderPass,
         uint cellId,