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

CHANGELOG.md

@@ -2,6 +2,22 @@
 
 All notable changes to **History** are listed here, newest first.
 
+## v0.39.0 — 2026-10-15 20:51
+- **#62: Ideology / form of government — a per-nation `ideology` + a `TurnResult.ideology` lever (coups / revolutions / reforms / constitutional changes) with a deterministic −5 stability dip and political narration.** Each nation may carry a free-form `ideology` label — its form of government ("democracy", "fascism", "military junta", …). The model changes it each turn via `ideology.changes`; each change names a target nation (id or name) and the new government type. The engine sets the label and applies a **deterministic** stability dip (a regime shift always unsettles a nation) — **no hidden randomness**, **additive** (no `db.ts` change — `ideology` is an optional `Nation` field; a pre-v0.39 row loads with it absent, i.e. "no recorded government"). 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.
+  - **Types (`shared/types.ts`).** `Nation.ideology?: string` (optional; `undefined`/absent = no recorded government).
+  - **Protocol (`shared/protocol.ts`).** New `IdeologyChange` (`{ target; to }` — `target` is a nation ref, `to` is the new form of government), `IdeologyOps` (`{ changes: IdeologyChange[] }`); `TurnResult.ideology` is **required**, placed between `leaders` and `markers`, default `{ changes: [] }`. New exported **`IDEOLOGY_STABILITY_EFFECT = −5`** (the deterministic stability dip of a regime shift). `nationForPrompt` now includes the nation's `ideology` (omitted when absent via `JSON.stringify`), so `buildUserPrompt` carries each nation's current government with no separate wiring.
+  - **Engine (`server/engine.ts`).**
+    - `validateIdeologyOps(raw)` — new exported, defensive validator (never throws): accepts a `{ changes: [...] }` object or a bare array; each change needs a non-empty `target` (trimmed, ≤120) and a non-empty, non-whitespace `to` (trimmed, ≤120) — anything else is dropped. Refs stay raw (resolved at apply time, like wars / hybrid / nuclear / leader ops).
+    - `applyIdeologyChange(next, op, geoOf?, actingTurn?)` — new, mirrors `applyLeaderChange` (single-stat, nation-target). Resolves the target (unknown / ambiguous → dropped, never thrown). On a valid change it sets `n.ideology = to` and applies `IDEOLOGY_STABILITY_EFFECT` (−5) to `n.stats.stability` (clamped 0–100) mirrored to every region the nation owns (`regionStats`), then re-derives the nation's stats (the same 0-region / no-entry guards as hybrid / economy / industry / leaders, so a 0-region nation keeps its directly-mutated value). Re-setting the **same** label is idempotent for the `ideology` field but still narrated and still dips (the shift just happened). Finally it appends a **`political`** narration event (`"<nation>'s government shifted to <to>"`). The change never moves territory (sole ownership is untouched).
+    - `applyTurnResult` — the ideology block runs **after `leaders` and before `markers`** (order: events → relations → territory → stateChanges → recompute → takeovers → wars → hybrid → economy → industry → nuclear → leaders → **ideology** → markers → nationOps).
+    - `isMeaningful` — a non-empty `ideology.changes` makes a turn meaningful.
+    - `validateTurnResult` — initializes and validates `ideology` (default `{ changes: [] }`).
+    - `buildSystemPrompt` — documents the `ideology` field (free-form label, the −5 dip, the "at most 1–2 per turn, narrated" rule) and contrasts it with a takeover (which RENAMES the nation) and a leader change (who is in charge); similar forms of government are a **soft, prompt-level compatibility nudge only** (alike ideologies tend to ally/trade, opposed ones tend to clash) — there is no engine gate behind it.
+    - `runTurn` — the "unclear" fallback carries `ideology: { changes: [] }`.
+  - **Stub (`server/stub.ts`).** `deterministicTurn` always returns `ideology: { changes: [] }` and the `StubPayload` nations type gains an optional `ideology` — the stub **never** changes an ideology, so the e2e (CI, `LLM_STUB=1`) is unaffected and the path is covered by unit tests only.
+  - **Tests.** New unit tests in `engine.test.ts`: `validateIdeologyOps` (`{changes}` object, bare array, empty/whitespace `to` drop, missing/whitespace target drop, malformed top-level, mixed batch keeps only valid, trim + 120-cap); `isMeaningful` (an ideology change is meaningful, empty ideology is not); `applyTurnResult` (a valid change → field set + 50→45 + `political` event + region mirror, other nation untouched; re-setting the same label → one dip, one event; a multi-region nation → every region dipped and stats re-derived; a target resolved by name as well as id; a 0-region nation keeps its directly-dipped stat; a dip clamped at 0; an unknown target and an ambiguous (two-nation-same-name) target → dropped without throwing); `buildUserPrompt` (a set ideology is stamped in the prompt nations, an absent one is omitted). `protocol.test.ts`: the `IDEOLOGY_STABILITY_EFFECT` constant is −5 and `nationForPrompt` includes/omits the `ideology` key in the JSON. Two `db.test.ts` round-trips: a legacy row with no ideology loads with it absent, and a set ideology round-trips through save/load.
+- **Version** bumped `0.38.0 → 0.39.0`.
+
 ## v0.38.0 — 2026-10-15 20:06
 - **#61: Named leaders — a per-nation `leader` + a `TurnResult.leaders` lever (assassination / death / appointment) with a deterministic stability effect and succession narration.** Each nation may carry a single named head of state (`Nation.leader`); the model changes it each turn via `leaders.changes`. The engine is **fully deterministic (no hidden randomness)** and **additive** (no `db.ts` change — `leader` is an optional `Nation` field; a pre-v0.38 row loads with it absent, i.e. "no leader").
   - **Types (`shared/types.ts`).** `Nation.leader?: { name: string }` (optional; `undefined`/absent = the nation has no leader).