feat: #65 sea control — 11th ability (v0.43.0)

Adds the sea ability: a fixed set of 12 named sea zones with sole-control
semantics, contest-by-higher-military, and a deterministic per-turn
+1 military/+1 economy bonus for each claimed zone. Durable (owns
GameState.seaZones), additive migration, stub-inert (e2e unaffected).

Fixes #65

Design note: Gitea #65 sketched a free-form 'naval' layer; the implemented
approved design is this richer 'sea' layer with a fixed zone set.

server/engine.ts

@@ -16,6 +16,7 @@ import type {
   RegionResources,
   RegionStats,
   RoundItem,
+  SeaZoneClaim,
   StatKey,
   TradeAgreement,
 } from '../shared/types';
@@ -104,6 +105,14 @@ export {
   MIGRATION_SOURCE_EFFECTS,
   MIGRATION_DESTINATION_EFFECTS,
   LARGE_INFLUX_STABILITY_DIP,
+  validateSeaOps,
+  applySeaControl,
+  applySeaZoneBonuses,
+  SEA_ZONE_BONUS,
+  SEA_ZONES,
+  SEA_ZONE_IDS,
+  isSeaZoneId,
+  seaZoneName,
 } from './abilities';
 
 // --- The LLM's getNeighbours tool (v0.21, #16 P2: contiguous region transfers) ---
@@ -376,6 +385,14 @@ export function buildUserPrompt(
    * key on any nation) when undefined.
    */
   nuclear?: Record<string, boolean>,
+  /**
+   * (v0.43.0, #65) The game's current sea-zone control (each a `{ zone, by }`
+   * pair of the fixed sea zones and their controlling nation id). Emitted
+   * verbatim (even when empty) so the model knows which of the 12 fixed sea
+   * zones each nation currently controls and can re-claim or contest them via
+   * `TurnResult.sea`. Omitted entirely when undefined.
+   */
+  seaZones?: SeaZoneClaim[],
 ): string {
   const player = state.nations[state.playerNationId];
   const playerName = player?.name ?? state.playerNationId;
@@ -485,6 +502,7 @@ export function buildUserPrompt(
     embargoes,
     nationResources,
     industryProjects,
+    seaZones,
   };
   Object.assign(payload, ABILITIES[0].payload(upCtx)); // takeovers → takeoverRisks
   if (noMansLand !== undefined) payload.unowned = noMansLand;
@@ -493,6 +511,7 @@ export function buildUserPrompt(
   Object.assign(payload, ABILITIES[2].payload(upCtx)); // hybrid → relations
   Object.assign(payload, ABILITIES[3].payload(upCtx)); // economy → trades, embargoes
   Object.assign(payload, ABILITIES[4].payload(upCtx)); // industry → resources, industry
+  Object.assign(payload, ABILITIES[10].payload(upCtx)); // sea → seaZones (always emitted)
   return JSON.stringify(payload, null, 2);
 }
 
@@ -633,6 +652,7 @@ export function validateTurnResult(
     ideology: { changes: [] },
     disasters: { events: [] },
     migration: { ops: [] },
+    sea: { control: [] },
     markers: { add: [], remove: [] },
   };
 
@@ -723,7 +743,7 @@ export function validateTurnResult(
   // list for the player to confirm/reject.
   result.nationOps = validateNationOps(o.nationOps);
 
-  // The 9 per-feature LLM abilities (v0.40.0, #67): each one's validate call
+  // The 11 per-feature LLM abilities (v0.40.0, #67): each one's validate call
   // is owned by its Ability module in the ABILITIES registry. The field's raw
   // value is passed through a.validate() which returns the validated field shape.
   for (const a of ABILITIES) {
@@ -917,6 +937,9 @@ export function applyTurnResult(
   // (v0.36, #59) active industry projects; a legacy/corrupt clone without the
   // field starts empty (the turn then only ever adds to it).
   next.industry = next.industry ?? [];
+  // (v0.43.0, #65) sea-zone control; a legacy/corrupt clone without the field
+  // starts empty (the turn then upserts this turn's claims into it).
+  next.seaZones = next.seaZones ?? [];
   const actingTurn = state.turn; // this action resolves the current turn
   next.turn = state.turn + 1; // then we advance to the next turn to play
   next.date = isDateLike(result.date) ? result.date : addDays(state.date, 2);
@@ -1594,6 +1617,9 @@ export async function runTurn(opts: {
     state.industry ?? [],
     // (v0.37.0, #60) per-nation nuclear capability (flag or rocket marker).
     nuclearCapability,
+    // (v0.43.0, #65) the current sea-zone control (always emitted — even when
+    // empty — so the model knows who controls which of the fixed sea zones).
+    state.seaZones ?? [],
   );
   const nudge =
     'Your previous output was invalid. Respond with ONLY the JSON object described above for this batch — no prose, no fences.';