test(@projects/@magic-civilization): 🚦 Rail-1 verify gate — no game-data transform logic in GDScript

Add tools/check-no-gdscript-sim-logic.py and wire it as verify step 18 (TOTAL
20→21). Fails if presentation GDScript (src/game/engine/src/**/*.gd) re-introduces
catalog yield aggregation (`yield_production += …`) or hand-built spec dicts
(`"yield_production": …`) — the exact drift class just moved to Rust. Verified to
flag the pre-7e2baa25d aggregation and pass clean on the current tree. Logic
belongs in the mc-* crates, reached via the GDExtension bridge (Rail 1).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/run/verify.sh

@@ -85,7 +85,7 @@ cmd_verify() {
         echo -e "${BLUE}─────────────────────────────────────────────────${NC}"
     }
 
-    local TOTAL=20
+    local TOTAL=21
 
     # Step 0 — Game data schema validation
     _verify_step 0 $TOTAL "game data JSON schemas" \
@@ -102,6 +102,12 @@ cmd_verify() {
     _verify_step 17 $TOTAL "no hardcoded applied UI colours" \
         python3 "$REPO_ROOT/tools/check-ui-color-sources.py"
 
+    # Step 18 — Rail-1 gate: no game-data transform/aggregation logic in
+    # presentation GDScript (catalog yield aggregation / hand-built spec dicts).
+    # Logic belongs in the mc-* Rust crates, reached via the GDExtension bridge.
+    _verify_step 18 $TOTAL "Rail-1: no sim logic in GDScript" \
+        python3 "$REPO_ROOT/tools/check-no-gdscript-sim-logic.py"
+
     # Step 16 — "Build output never under src/" invariant.
     # Rule source: .claude/instructions/build-output-locations.md.
     _verify_step 16 $TOTAL "no build output under src/" \

tools/check-no-gdscript-sim-logic.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+"""Rail-1 guard: no game-data transform/aggregation logic in GDScript.
+
+GDScript is presentation only. Simulation logic — stat aggregation, catalog
+construction, balance math — lives in Rust (the `mc-*` crates) and is reached
+through the GDExtension bridge. This gate fails if presentation GDScript
+re-introduces the kind of game-data transform that was deliberately moved to
+Rust, so the single-source-of-truth (Rail 1 + Rail 2) cannot silently regress
+the way the unit/building catalogs did.
+
+Flagged in `src/game/engine/src/**/*.gd` (presentation; tests are excluded):
+  * yield aggregation   — `yield_production += ...`  (summing sim yields)
+  * spec construction    — `"yield_production": ...`  (hand-building a catalog spec)
+
+Reach for the canonical Rust transform instead:
+  `mc_ai::tactical::parse_unit_catalog` / `parse_building_catalog`, exposed via
+  `GdItemSystem.{parse_unit_catalog_json, aggregate_building_catalog_json}`, and
+  delegate from GDScript.
+
+Usage:
+  tools/check-no-gdscript-sim-logic.py          # report; exit 1 if violations
+"""
+from __future__ import annotations
+
+import re
+import sys
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+SRC = REPO_ROOT / "src" / "game" / "engine" / "src"
+
+# The scalar yield channels the tactical catalogs aggregate. Kept in sync with
+# `TacticalBuildingSpec` (mc-core/tactical_types.rs).
+_YIELD = r"(food|production|gold|science|culture|defense|happiness|gpp|great_work_slots)"
+
+_PATTERNS: list[tuple[re.Pattern[str], str]] = [
+    # `yield_production += ...` or `item["yield_production"] += ...`
+    (re.compile(rf"yield_{_YIELD}\b[\"\]\s]*\+="),
+     "yield aggregation — sum sim yields in Rust, not GDScript"),
+    # `"yield_production": ...` — a catalog spec dict built by hand.
+    (re.compile(rf'"yield_{_YIELD}"\s*:'),
+     "catalog spec dict constructed in GDScript — use the Rust transform"),
+]
+
+
+def main() -> int:
+    if not SRC.is_dir():
+        print(f"error: GDScript source dir not found: {SRC}", file=sys.stderr)
+        return 2
+
+    violations: list[tuple[str, int, str, str]] = []
+    for path in sorted(SRC.rglob("*.gd")):
+        text = path.read_text(encoding="utf-8", errors="replace")
+        for lineno, line in enumerate(text.splitlines(), start=1):
+            stripped = line.strip()
+            # Skip comment lines (doc comments legitimately name these fields).
+            if stripped.startswith("#"):
+                continue
+            for rx, why in _PATTERNS:
+                if rx.search(line):
+                    rel = path.relative_to(REPO_ROOT)
+                    violations.append((str(rel), lineno, why, stripped))
+
+    if violations:
+        print(f"Rail-1 violation: {len(violations)} game-data transform site(s) in presentation GDScript:")
+        for rel, lineno, why, stripped in violations:
+            print(f"  {rel}:{lineno}  [{why}]")
+            print(f"      {stripped}")
+        print(
+            "\nGDScript is presentation only (Rail 1). Move the logic into a Rust\n"
+            "transform (mc_ai::tactical::parse_unit_catalog / parse_building_catalog)\n"
+            "and delegate from GDScript via GdItemSystem."
+        )
+        return 1
+
+    print("OK: no game-data transform logic in presentation GDScript (Rail 1)")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())