docs(render): record the retail land-cell draw order from the cathedral captures (S3 chunk 3 oracle)

Frame 2 of both cathedral transcripts: one LS, then LC/SC in strict
per-cell alternation, blocks far-to-near with the diagonal interleave
from the Chebyshev-10 ring inward, far blocks at one cell per block, and
SC for all 64 cells of a near block while LC fires only for in-view
cells. This is the interleave chunk 3 ports and the transcript pins.

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

docs/research/2026-09-01-overhaul/s3-walk-ownership-map.md

@@ -164,6 +164,22 @@ Lead verifies every finding against the source before an edit (S2 precedent:
   1,735 AM / 3,570 FL / 35 PM / 19 PC). NOTE: the kit README expected
   `DI f4180106` (FW0's arrival still); the live client reported `f4180108`,
   the stair-chamber cell — the owner's actual standing cell, recorded as-is.
+- **Chunk-3 oracle read off the two cathedral transcripts (frame 2 of each,
+  viewer in `f4180108`):** after the root `DI`/`DC` and ONE `LS`, retail emits
+  `LC <cell>` then `SC <cell>` for every admitted land cell in STRICT alternation
+  (`LSLSLS…`, never two `LC` in a row) — `DrawLandCell` then `DrawSortCell` per
+  cell, exactly the per-cell interleave chunk 3 ports. Block order is far-to-near
+  from the far corner: rows `y=00…0d` each walked `x=fe→f6`, then from the
+  Chebyshev-10 ring inward the column and row interleave diagonally
+  (`fe0e fd0e fe0f fc0e fe10 fb0e fe11 …`), ending at `… f417 f318 f418`; the
+  exact rule is `LScape::calc_draw_order`'s and the transcript pins it. Far
+  blocks draw ONE cell (`xx000001`, side count 1); near the viewer `SC` fires for
+  all 64 cells of the block while `LC` fires only for the in-view ones (`f418`:
+  16 LC / 64 SC; `f417`: 56 / 64; `f318`: 3 / 64) — `DrawSortCell` runs under
+  `alwaysDrawObjects` for every cell of an in-view block, `DrawLandCell` only for
+  in-view cells (`RenderDeviceD3D::DrawBlock` @0x005a19d9 — chunk 3 re-reads the
+  exact gate). Per frame: leak pose 531 LC / 757 SC / 16 BLD; arrival pose
+  533 LC / 698 SC / 14 BLD.
 - Remaining poses per the kit README: `holtburg-doorway-still`,
   `terrace-edge`, `foundry-deep`.