Record board dimensions (7.5in square) and absence of errata sheet

Owner-measured: sector boards are 7.5in to a side (1.5in per space);
no errata sheet in the 6e box. Closes the physical checklist except
the optional counter-sheet inventory.

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

research/boards-6e.md

@@ -68,8 +68,9 @@ are saved in `research/images/`.
 - Boards are **single-sided**, black-and-white line art in 6e. *(Single-sidedness:
   LIKELY — no photo or listing shows a printed back; the double-sided "classic/new"
   boards are an 8th-edition (FFG) feature.)*
-- Physical size: UNCERTAIN. A fan who reproduced them printed at 7.5 in square; the actual
-  Chessex boards' dimensions need measuring from the physical copy.
+- Physical size: **CONFIRMED 7.5 in square** (owner-measured, 2026-08-15; 1.5 in per space).
+  The fan reproduction's 7.5 in print size was exactly right. The owner's box also contains
+  **no errata sheet** (unlike the 5th edition).
 
 ## 3. The six maze layouts (CONFIRMED, with caveats noted)