tests: scenario rotation integrity check (every 10 rounds)

Combat.scenario.test.js: per-10-round assertion - turnOrderIds no dup,
currentTurnParticipantId in turnOrderIds. 299/299 phases pass.

NOTE: scenario runs against firebase MOCK. Mock updateDoc merges correctly
(real ws adapter would clobber per BUG-4 class). So check validates mock
shape, not adapter translation. Layer 2 (ws-contract) covers adapter.

src/tests/Combat.scenario.test.js

@@ -256,6 +256,22 @@ test('full 100-round combat scenario', async () => {
   for (let r = 1; r <= ROUNDS; r++) {
     await recordAsync(`round ${r} nextTurn`, () => nextTurn());
 
+    // rotation integrity: turnOrderIds no dup, currentTurn valid
+    if (r % 10 === 0) {
+      record(`round ${r} rotation-check`, () => {
+        const enc = currentEncDoc();
+        if (!enc) throw new Error('no encounter doc');
+        const order = enc.turnOrderIds || [];
+        const uniq = new Set(order);
+        if (uniq.size !== order.length) {
+          throw new Error(`turnOrderIds dup: ${JSON.stringify(order)}`);
+        }
+        if (enc.currentTurnParticipantId && !order.includes(enc.currentTurnParticipantId)) {
+          throw new Error(`currentTurn ${enc.currentTurnParticipantId} not in turnOrderIds`);
+        }
+      });
+    }
+
     // damage front monster every other round
     if (r % 2 === 0) record(`round ${r} damage OrcBoss`, () => applyDamage('OrcBoss', 3));
     if (r % 3 === 0) record(`round ${r} heal Cleric`, () => applyHeal('Cleric', 2));