Add verified engine data layer: cards.json, boards.json, rules reference

cards.json: 220 cards across base/Exp1/Exp2 with official 6E quantities
from Eric's rulebook (base = exactly 125, Exp1 = exactly 75), verbatim
text for all but two cards, FAQ rulings, and per-card verification
flags. boards.json: all six sector layouts, now physically verified
against Eric's board photos with zero corrections (research/
boards-verification.md), plus 2-8 player setup configurations.
rules-notes.md is the engine implementer's reference; VERIFICATION.md
tracks the few remaining spot-checks (Butt-Head and Mega-Monster card
text foremost).

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

research/boards-6e.md

@@ -59,8 +59,11 @@ are saved in `research/images/`.
   effect).
 - **Doors:** drawn as a wooden plank with hinge/knob circles filling a wall gap. Each
   layout has **1 or 2 printed doors** (8 doors across the 6 boards).
-- **No other special spaces.** Each space has a small centering dot (decorative). There are
-  no numbered spaces, portals, or terrain printed on the Chessex boards — everything else
+- **No other special spaces.** ~~Each space has a small centering dot (decorative).~~
+  **CORRECTION (2026-08-15, from owner's photos):** the physical 6e boards have NO centering
+  dots — the dots were an artifact of the fan redraws. (Consistent with the designer note
+  that 6e dropped the LOS center dots; the rulebook text still defines LOS center-to-center.)
+  There are no numbered spaces, portals, or terrain printed on the Chessex boards — everything else
   (thornbushes, rocks, created walls/doors, etc.) is tokens placed during play.
 - 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"