refactor(#74) P1: capture golden prompt baselines for the ability-module refactor

Adds deterministic golden fixtures (server/abilities/goldens/) pinning the
EXACT output of buildSystemPrompt (no-tool + tool modes) and buildUserPrompt
for a fixed wwii-1939 preset plus a crafted state that exercises every
optional payload branch (regions, frontier, frontierMilitary, takeoverRisks,
unowned, markers, wars, relations, trades, embargoes, resources, industry).

These are the target: the v0.40.0 modular ability registry (P2-P5) must
reproduce these byte-for-byte. Part of #74.

server/abilities/goldens/user.txt

@@ -0,0 +1,209 @@
+{
+  "state": {
+    "turn": 4,
+    "date": "1940-02-14",
+    "playerNationId": "a1",
+    "nations": {
+      "a1": {
+        "id": "a1",
+        "name": "Alpha",
+        "type": "major",
+        "stats": {
+          "military": 60,
+          "economy": 55,
+          "stability": 70,
+          "population": 80
+        },
+        "territory": [
+          "a-r1",
+          "a-r2"
+        ],
+        "relations": {
+          "b2": "ally",
+          "c3": "rival"
+        },
+        "leader": {
+          "name": "Alpha Leader"
+        },
+        "ideology": "democracy",
+        "nuclear": true
+      },
+      "b2": {
+        "id": "b2",
+        "name": "Bravo",
+        "type": "major",
+        "stats": {
+          "military": 75,
+          "economy": 40,
+          "stability": 20,
+          "population": 30
+        },
+        "territory": [
+          "b-r1",
+          "b-r2"
+        ],
+        "relations": {
+          "a1": "ally"
+        },
+        "ideology": "fascism",
+        "nuclear": false
+      },
+      "c3": {
+        "id": "c3",
+        "name": "Charlie",
+        "type": "major",
+        "stats": {
+          "military": 30,
+          "economy": 35,
+          "stability": 80,
+          "population": 20
+        },
+        "territory": [
+          "c-r1"
+        ],
+        "relations": {
+          "a1": "rival"
+        },
+        "nuclear": false
+      }
+    },
+    "recentEvents": []
+  },
+  "playerActions": [
+    "Rearm the northern border",
+    {
+      "to": "b2",
+      "message": "We can still talk terms, no?"
+    }
+  ],
+  "pending": [
+    {
+      "kind": "action",
+      "text": "Rearm the northern border"
+    },
+    {
+      "kind": "diplomacy",
+      "to": "b2",
+      "text": "We can still talk terms, no?"
+    }
+  ],
+  "roundInstruction": "This period the player (Alpha) takes the following actions and sends the following diplomatic messages: [\"Rearm the northern border\",{\"to\":\"b2\",\"message\":\"We can still talk terms, no?\"}]. Simulate the combined consequences across all nations and advance the world by one period. Return a single TurnResult.",
+  "playerRegionStats": {
+    "a-r1": {
+      "military": 60,
+      "economy": 55,
+      "stability": 70,
+      "population": 80
+    },
+    "a-r2": {
+      "military": 58,
+      "economy": 53,
+      "stability": 72,
+      "population": 78
+    }
+  },
+  "regions": {
+    "a-r1": "Alpha North (US)",
+    "a-r2": "Alpha South (US)",
+    "b-r1": "Bravo Plain (RU)",
+    "b-r2": "Bravo Coast (RU)",
+    "c-r1": "Charlie Isle (FR)",
+    "x-unowned": "X Released (UN)"
+  },
+  "frontier": [
+    "b-r1"
+  ],
+  "frontierMilitary": [
+    "[Your military: 60] vs [Bravo: 75] — a direct invasion could succeed"
+  ],
+  "takeoverRisks": [
+    "Bravo (stability 20, a gathering is in progress)"
+  ],
+  "unowned": [
+    "x-unowned"
+  ],
+  "markers": [
+    {
+      "id": "mk0001",
+      "type": "gathering",
+      "name": "Bravo Rally",
+      "regionKey": "b-r1",
+      "owner": "b2"
+    },
+    {
+      "id": "mk0002",
+      "type": "rocket",
+      "name": "Charlie Silo",
+      "regionKey": "c-r1",
+      "owner": "c3"
+    },
+    {
+      "id": "mk0003",
+      "type": "capital",
+      "name": "Alpha Cap",
+      "regionKey": "a-r1",
+      "owner": "a1"
+    }
+  ],
+  "wars": [
+    {
+      "id": "w1",
+      "sides": [
+        "a1",
+        "b2"
+      ],
+      "aims": [
+        "control the border"
+      ]
+    },
+    {
+      "id": "w2",
+      "sides": [
+        "b2",
+        "c3"
+      ]
+    }
+  ],
+  "relations": {
+    "b2": "ally",
+    "c3": "rival"
+  },
+  "trades": [
+    {
+      "a": "a1",
+      "b": "c3"
+    }
+  ],
+  "embargoes": [
+    {
+      "from": "a1",
+      "target": "b2"
+    }
+  ],
+  "resources": {
+    "a1": {
+      "oil": 0.5,
+      "iron": 0.2,
+      "food": 0.3,
+      "industry": 0.8
+    },
+    "b2": {
+      "oil": 0.1,
+      "iron": 0.9,
+      "food": 0.1,
+      "industry": 0.2
+    },
+    "c3": {
+      "oil": 0.2,
+      "iron": 0.3,
+      "food": 0.7,
+      "industry": 0.4
+    }
+  },
+  "industry": [
+    {
+      "regionKey": "a-r1",
+      "type": "industry"
+    }
+  ]
+}