feat(#62): ideology / government-type change (v0.39.0)

Add a per-nation free-form ideology (form of government) field and a
TurnResult.ideology lever (coups / revolutions / reforms / constitutional
changes) with a deterministic -5 stability dip and political narration.

- shared/types.ts: Nation.ideology?: string (optional/additive)
- shared/protocol.ts: IdeologyChange / IdeologyOps, IDEOLOGY_STABILITY_EFFECT
  = -5, TurnResult.ideology (required, between leaders and markers),
  nationForPrompt now carries ideology
- server/engine.ts: validateIdeologyOps (exported, never throws),
  applyIdeologyChange (resolve -> set field -> -5 dip mirrored to regions +
  re-derived -> political event), ideology block in applyTurnResult after
  leaders / before markers, isMeaningful + validateTurnResult + system prompt
  + runTurn unclear fallback
- server/stub.ts: StubPayload gains ideology; deterministicTurn returns
  ideology: { changes: [] } (never changes one, e2e unaffected)
- Tests: engine.test.ts (validate / isMeaningful / applyTurnResult /
  buildUserPrompt), protocol.test.ts (constant + nationForPrompt),
  db.test.ts (legacy load + round-trip); every TurnResult fixture updated
- package.json -> 0.39.0; CHANGELOG v0.39.0 entry

shared/protocol.ts

@@ -510,6 +510,44 @@ export const LEADER_STABILITY_EFFECT: Record<LeaderCause, number> = {
   appointed: 0,
 };
 
+// --- Ideology / form of government (v0.39, #62) ------------------------------
+//
+// Each nation may carry a free-form `ideology` label — its form of
+// government ("democracy", "fascism", "military junta", …). The LLM changes it
+// each turn via `TurnResult.ideology`: a change names a target nation (id or
+// name) and the new government type. The engine sets the nation's `ideology`
+// and applies a DETERMINISTIC stability dip (see `IDEOLOGY_STABILITY_EFFECT`
+// below) — a regime shift always unsettles a nation — no hidden randomness.
+// It is a third, independent axis next to `leader` (who is in charge) and the
+// v0.32.0 takeover (which renames the nation): the id, name, territory,
+// relations, and the leader all stay valid, only the form of government and
+// stability move.
+
+/** A single ideology change: the target nation and its new form of government. */
+export interface IdeologyChange {
+  /** The target nation, by id or name (resolved by the shared resolver). */
+  target: string;
+  /** The new form of government (a free-form label, e.g. "democracy"). */
+  to: string;
+}
+
+/** The ideology-ops block of a `TurnResult`. Required; default `{ changes: [] }`. */
+export interface IdeologyOps {
+  changes: IdeologyChange[];
+}
+
+/**
+ * The deterministic stability effect of an ideology change (v0.39, #62). A
+ * regime shift (a coup, a revolution, a reform, a constitutional change)
+ * unsettles the nation: a small −5 dip applied to the target's `stability`
+ * (clamped 0–100), mirrored to its `regionStats`, and its derived stats
+ * re-derived afterwards. Applied the same way a leader-cause effect is —
+ * re-setting the SAME ideology still dips (the shift just happened, even if
+ * the label does not change) but is idempotent for the `ideology` field
+ * itself.
+ */
+export const IDEOLOGY_STABILITY_EFFECT: number = -5;
+
 // --- Nuclear / WMD effect math (v0.37, #60) ----------------------------------
 //
 // A nuclear strike is a DETERMINISTIC, devastating stat collapse — there is no
@@ -694,6 +732,23 @@ export interface TurnResult {
    * no leader replacement). Required; default `{ changes: [] }`.
    */
   leaders: LeaderOps;
+  /**
+   * (v0.39, #62) Ideology (form of government) changes this turn. Each
+   * change names a target nation (id or name) and its new form of
+   * government — a free-form label such as "democracy", "fascism", or
+   * "military junta". Applied directly by `applyTurnResult` (like leaders /
+   * hybrid / economy): the target's `ideology` is set to the new label, a
+   * small, deterministic stability dip (`IDEOLOGY_STABILITY_EFFECT`, −5) is
+   * applied (clamped, mirrored to the nation's regions, re-derived), and a
+   * `political` narration event is appended. Re-setting the same label is
+   * idempotent for the field (still narrated, still dips). Unknown /
+   * ambiguous targets and empty labels are dropped, never thrown; the
+   * change never moves territory (sole ownership is untouched). Distinct
+   * from a takeover (which renames the nation) and from a leader change
+   * (who is in charge). At most 1–2 per turn, each narrated in `events`.
+   * Required; default `{ changes: [] }`.
+   */
+  ideology: IdeologyOps;
   /**
    * (v0.27, #44) Map-marker ops this turn. `add` places new named markers
    * (the engine positions each at its region's centroid + a small
@@ -1007,6 +1062,7 @@ export function nationForPrompt(n: Nation) {
     territory: n.territory,
     relations: n.relations,
     leader: n.leader,
+    ideology: n.ideology,
   };
 }
 

shared/types.ts

@@ -88,6 +88,18 @@ export interface Nation {
    * each change carries a deterministic stability effect + a narration event.
    */
   leader?: { name: string };
+  /**
+   * The nation's current form of government (v0.39, #62) — a free-form label
+   * such as `"democracy"`, `"fascism"` or `"military junta"`. Optional — a
+   * legacy game (or a nation the LLM has never given an ideology to) has none,
+   * which is the "no recorded government" baseline. The LLM changes it via
+   * `TurnResult.ideology` (coups / revolutions / reforms / constitutional
+   * changes, see `IdeologyChange` in `protocol.ts`); each change carries a
+   * deterministic stability dip + a political narration event. Distinct from
+   * the v0.32.0 takeover (which renames the nation) and from `leader` (who is
+   * in charge): only the form of government and stability move.
+   */
+  ideology?: string;
 }
 
 /** Categories a narrative event can take. */