fix(render): S3 chunk 2 review follow-ups

- delete the ACDREAM_PROBE_CATHEDRAL_SKIP_SEALS discriminator (member, read
  site, launch-options row): its investigation is closed by the retail
  axiom, and the review found it had silently gained a second effect through
  the seal count (a skipped seal also suppressed the next depth clear);
- the interior PView's draw_landscape is now wired explicitly (RenderDeviceD3D::Init
  0x0059efb0), so the two-PView pin asserts wiring, not a default;
- the two backend seam comments name retail's clear gate;
- the counter doc states the Collect/Replay consume/re-arm split and why it
  has no retail analogue.

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

src/AcDream.Core/Rendering/RenderingDiagnostics.cs

@@ -119,16 +119,6 @@ public static class RenderingDiagnostics
     public static bool ProbeCathedralSkipStairBuildingPunch { get; set; } =
         Environment.GetEnvironmentVariable("ACDREAM_PROBE_CATHEDRAL_SKIP_PUNCH") == "1";
 
-    /// <summary>
-    /// Temporary cathedral discriminator: suppresses only the true-depth exit
-    /// seals authored by the two cells that meet at the floating-stair seam.
-    /// Both portal polygons lie on world Y ~= 24 and span the reported moving
-    /// triangle. This is a binary visual experiment only; normal production
-    /// behavior is unchanged while the flag is unset.
-    /// </summary>
-    public static bool ProbeCathedralSkipFloatingStairSeals { get; set; } =
-        Environment.GetEnvironmentVariable("ACDREAM_PROBE_CATHEDRAL_SKIP_SEALS") == "1";
-
     /// <summary>
     /// Temporary cathedral carrier discriminator: suppresses only the visible
     /// EnvCell shells for cells 0xF4180107 and 0xF4180112. This deliberately