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/shared/ipc/contracts.players.test.ts

@@ -0,0 +1,17 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import path from 'node:path';
+import test from 'node:test';
+import { fileURLToPath } from 'node:url';
+
+const here = path.dirname(fileURLToPath(import.meta.url));
+const contractsPath = path.join(here, 'contracts.ts');
+
+void test('contracts: players and sceneNpcTokensSession channels exist', () => {
+  const src = fs.readFileSync(contractsPath, 'utf8');
+  assert.match(src, /players:\s*\{/);
+  assert.match(src, /list:\s*'players\.list'/);
+  assert.match(src, /upsertProgress:\s*'players\.upsertProgress'/);
+  assert.match(src, /sceneNpcTokensSession:\s*\{/);
+  assert.match(src, /npcTokens\?:\s*SceneNpcToken\[\]/);
+});