fix(cypher-executor): FOREACH iter plural 變體 (entity → entities)

舊 getIterableFromContext 只試 'key+s'，遇 irregular plural 不命中：
  entity + s = entitys ≠ entities (Claude 真實 output)

加變體：
  - key + 's'                       (paragraph → paragraphs)
  - key.replace(/y$/, 'ies')        (entity → entities)
  - key.replace(/(s|x|z|ch|sh)$/, '$1es')  (box → boxes)
  - key (singular fallback)

對應 mira wiki_synthesis V3 multi-entity 升級需求。

cypher-executor/src/graph-executor.ts

@@ -654,22 +654,30 @@ function evaluateCondition(condition: string, context: unknown): boolean {
 
 function getIterableFromContext(context: unknown, key: string): unknown[] {
   if (!context || typeof context !== 'object') return [];
-  const plural = key + 's';
+  // 多種 plural 變體：entity → entities / paragraph → paragraphs / box → boxes / 等
+  // 2026-05-17：原本只試 key+'s'，'entity+s=entitys' ≠ 'entities' 無法命中，加 irregular
+  const variants = [
+    key + 's',                       // paragraph → paragraphs
+    key.replace(/y$/, 'ies'),        // entity → entities
+    key.replace(/(s|x|z|ch|sh)$/, '$1es'),  // box → boxes
+    key,                              // singular fallback
+  ];
   const obj = context as Record<string, unknown>;
+
   // 先看 top-level（最常見）
-  let items = obj[plural] ?? obj[key];
+  for (const v of variants) {
+    if (Array.isArray(obj[v])) return obj[v] as unknown[];
+  }
+
   // 若找不到，掃一層內部 object 看 nested（巢狀 FOREACH 場景：
   // 外層 FOREACH 把 paragraph 注入 ctx，內層 FOREACH 要找 paragraph.triplets）
-  if (!Array.isArray(items)) {
-    for (const v of Object.values(obj)) {
-      if (v !== null && typeof v === 'object' && !Array.isArray(v)) {
-        const nested = (v as Record<string, unknown>)[plural] ?? (v as Record<string, unknown>)[key];
-        if (Array.isArray(nested)) {
-          items = nested;
-          break;
+  for (const val of Object.values(obj)) {
+    if (val !== null && typeof val === 'object' && !Array.isArray(val)) {
+      for (const v of variants) {
+        const nested = (val as Record<string, unknown>)[v];
+        if (Array.isArray(nested)) return nested;
       }
     }
   }
-  }
-  return Array.isArray(items) ? items : [];
+  return [];
 }