feat(players): app Players library and circular NPC tokens on scenes

Add userData players/teams, scene npcTokens with hex-inscribed sizing, session scale synced to presentation, and Playwright e2e coverage.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/main/players/sceneNpcTokensSessionStore.test.ts

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+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import { DEFAULT_NPC_TOKEN_SESSION_SCALE } from '../../shared/types/appPlayers';
+
+import { SceneNpcTokensSessionStore } from './sceneNpcTokensSessionStore';
+
+void test('SceneNpcTokensSessionStore move and reset', () => {
+  const store = new SceneNpcTokensSessionStore();
+  const s1 = store.dispatch({ kind: 'move', placementId: 'a', nx: 0.2, ny: 0.3 });
+  assert.equal(s1.byPlacementId.a?.nx, 0.2);
+  assert.equal(s1.revision, 2);
+  const s2 = store.dispatch({ kind: 'move', placementId: 'a', nx: 0.2, ny: 0.3 });
+  assert.equal(s2.revision, s1.revision); // no-op
+  const s3 = store.reset();
+  assert.deepEqual(s3.byPlacementId, {});
+  assert.equal(s3.scale, DEFAULT_NPC_TOKEN_SESSION_SCALE);
+  assert.ok(s3.revision > s1.revision);
+});
+
+void test('SceneNpcTokensSessionStore setScale', () => {
+  const store = new SceneNpcTokensSessionStore();
+  const s1 = store.dispatch({ kind: 'setScale', scale: 1.5 });
+  assert.equal(s1.scale, 1.5);
+  store.dispatch({ kind: 'move', placementId: 'a', nx: 0.1, ny: 0.2 });
+  const s2 = store.dispatch({ kind: 'setScale', scale: 0.1 });
+  assert.equal(s2.scale, 0.4); // clamped min
+  assert.ok(s2.byPlacementId.a);
+  const s3 = store.reset();
+  assert.equal(s3.scale, DEFAULT_NPC_TOKEN_SESSION_SCALE);
+  assert.deepEqual(s3.byPlacementId, {});
+});