refactor: rename core-public -> engine-public; fold helpers in; drop shared

Tighten the package model around the determinism invariant: everything the
engine imports must itself be deterministic.

- Rename core-public -> engine-public (package, dir, `engine-public/*` alias,
  all 118 import sites). It is the deterministic public surface the engine
  depends on and that client/server also use.
- Move the pure formatting helpers (renderNumber/renderTroops) from shared
  into engine-public/format — the engine uses them and they're deterministic.
- Drop the now-empty shared package (and its alias). `shared` was intended for
  client/server-shared, engine-forbidden code; there is none yet, so it is
  removed and can be re-added when such code appears.

Final graph: engine-public (leaf) <- engine <- {client, server};
client/server also -> engine-public.

Verified: tsc clean; 1364 + 65 tests pass; prod build succeeds; engine-public
is a leaf; engine has no client/server imports. Lockfile regenerated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/core/GameRunner.test.ts

@@ -1,7 +1,7 @@
 import { NationExecution } from "engine/execution/NationExecution";
 import { SpawnExecution } from "engine/execution/SpawnExecution";
 import { Cell, Nation, PlayerInfo, PlayerType } from "engine/game/Game";
-import { GameConfig, GameID } from "core-public/Schemas";
+import { GameConfig, GameID } from "engine-public/Schemas";
 import { setup } from "../util/Setup";
 import { executeTicks } from "../util/utils";
 

tests/core/executions/SAMLauncherExecution.test.ts

@@ -9,7 +9,7 @@ import {
   PlayerType,
   UnitType,
 } from "engine/game/Game";
-import { GameID } from "core-public/Schemas";
+import { GameID } from "engine-public/Schemas";
 import { setup } from "../../util/Setup";
 import { constructionExecution, executeTicks } from "../../util/utils";
 

tests/core/game/GameImpl.test.ts

@@ -1,4 +1,4 @@
-import { GameID } from "core-public/Schemas";
+import { GameID } from "engine-public/Schemas";
 import { AttackExecution } from "engine/execution/AttackExecution";
 import { SpawnExecution } from "engine/execution/SpawnExecution";
 //import { TransportShipExecution } from "engine/execution/TransportShipExecution";

tests/core/game/TrainStation.test.ts

@@ -15,7 +15,7 @@ import {
 } from "engine/game/Game";
 import { Cluster, TrainStation } from "engine/game/TrainStation";
 import { UserSettings } from "engine/game/UserSettings";
-import { GameConfig } from "core-public/Schemas";
+import { GameConfig } from "engine-public/Schemas";
 
 vi.mock("engine/game/Game");
 vi.mock("engine/execution/TrainExecution");

tests/core/pathfinding/_fixtures.ts

@@ -11,7 +11,7 @@ import {
 import { createGame as createGameImpl } from "engine/game/GameImpl";
 import { GameMapImpl } from "engine/game/GameMap";
 import { UserSettings } from "engine/game/UserSettings";
-import { GameConfig } from "core-public/Schemas";
+import { GameConfig } from "engine-public/Schemas";
 import { TestConfig } from "../../util/TestConfig";
 
 export const W = "W"; // Water