Add Hanzhong gate scenario

docs/DATA_MODEL.md

@@ -50,6 +50,7 @@ data/scenarios/036_weishui_crossing.json
 data/scenarios/037_guanzhong_foothold.json
 data/scenarios/038_ma_chao_retreat.json
 data/scenarios/039_hanzhong_approach.json
+data/scenarios/040_hanzhong_gate.json
 ```
 
 ## Campaign
@@ -101,7 +102,8 @@ The campaign file defines scenario order, resource paths, and officers who are a
     { "id": "036_weishui_crossing", "title": "Weishui Crossing", "path": "res://data/scenarios/036_weishui_crossing.json" },
     { "id": "037_guanzhong_foothold", "title": "Guanzhong Foothold", "path": "res://data/scenarios/037_guanzhong_foothold.json" },
     { "id": "038_ma_chao_retreat", "title": "Ma Chao Retreat", "path": "res://data/scenarios/038_ma_chao_retreat.json" },
-    { "id": "039_hanzhong_approach", "title": "Hanzhong Approach", "path": "res://data/scenarios/039_hanzhong_approach.json" }
+    { "id": "039_hanzhong_approach", "title": "Hanzhong Approach", "path": "res://data/scenarios/039_hanzhong_approach.json" },
+    { "id": "040_hanzhong_gate", "title": "Hanzhong Gate", "path": "res://data/scenarios/040_hanzhong_gate.json" }
   ]
 }
 ```

docs/ROADMAP.md

@@ -21,7 +21,7 @@
 - Destination victory conditions and objective map markers exist.
 - Turn-limit conditions and HUD turn-limit display exist.
 - Victory reward summary is visible.
-- Next-battle flow exists across the current thirty-nine-scenario campaign.
+- Next-battle flow exists across the current forty-scenario campaign.
 - Campaign completion and new-campaign reset exist.
 - Reward inventory can be brought into the next battle.
 
@@ -52,7 +52,7 @@
 - Party roster persistence has a first save-file skeleton.
 - Level, experience, and equipment persistence.
 - Chapter selection and save/load.
-- Linear thirty-nine-scenario campaign order exists.
+- Linear forty-scenario campaign order exists.
 - Save reset exists.
 - Victory rewards, consumable counts, equipment stock, and equipped gear persist.
 - A basic pre-battle shop with scenario-specific stock exists. Sell-back and richer item management are still planned.
@@ -99,6 +99,7 @@
 - Thirty-seventh-scenario content exists with Guanzhong foothold pressure, Ma Chao's rearguard, split-alliance tension, and 036 branch reactions.
 - Thirty-eighth-scenario content exists with Ma Chao retreat pressure, Guanzhong commandery stakes, western road pursuit, and 037 branch reactions.
 - Thirty-ninth-scenario content exists with Hanzhong approach pressure, Zhang Lu's border guard, mountain-gate stakes, and 038 branch reactions.
+- Fortieth-scenario content exists with Hanzhong gate pressure, Zhang Lu's mountain guard, pass-road siege stakes, 039 branch reactions, and submission or pacification follow-up flags.
 
 ## Milestone 5: Presentation