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/abilities/index.ts

@@ -1,8 +1,8 @@
 // The ordered LLM-ability registry.
 //
-// `ABILITIES` is the single source of truth for the 10 per-feature LLM abilities.
+// `ABILITIES` is the single source of truth for the 11 per-feature LLM abilities.
 // The engine iterates it in this order:
-//   takeovers → wars → hybrid → economy → industry → nuclear → leaders → ideology → disasters → migration
+//   takeovers → wars → hybrid → economy → industry → nuclear → leaders → ideology → disasters → migration → sea
 // for (a) the system-prompt schema lines + constraint bullets, (b) the per-ability
 // validate calls inside validateTurnResult, (c) the payload fields in buildUserPrompt,
 // (d) the ordered apply block inside applyTurnResult, (e) the isMeaningful check,
@@ -24,10 +24,11 @@ import { leaders } from './leaders';
 import { ideology } from './ideology';
 import { disasters } from './disasters';
 import { migration } from './migration';
+import { sea } from './sea';
 import type { Ability, AbilityField } from './types';
 
 /**
- * The 10 per-feature LLM abilities in their canonical apply order.
+ * The 11 per-feature LLM abilities in their canonical apply order.
  * The order matters: it determines the order of the schema lines in the
  * system prompt, the order of the validate calls, the order of the apply
  * steps, and the order of the payload fields in the user prompt. New
@@ -45,6 +46,7 @@ export const ABILITIES: readonly Ability<AbilityField>[] = [
   ideology,
   disasters,
   migration,
+  sea,
 ];
 
 // ── type re-exports ────────────────────────────────────────────────────────────
@@ -158,3 +160,16 @@ export {
   MIGRATION_DESTINATION_EFFECTS,
   LARGE_INFLUX_STABILITY_DIP,
 } from './migration';
+
+// ── sea ──────────────────────────────────────────────────────────────────────
+
+export {
+  validateSeaOps,
+  applySeaControl,
+  applySeaZoneBonuses,
+  SEA_ZONE_BONUS,
+  SEA_ZONES,
+  SEA_ZONE_IDS,
+  isSeaZoneId,
+  seaZoneName,
+} from './sea';