fix(mira): wikilink autocomplete 5s cache + 開下拉時 refetch

leo 反饋：30s TTL 太久，wiki_synthesis 後台跑出新 entity，autocomplete 撈不到。
- TTL 30s → 5s
- WikilinkAutocomplete 在 matchInfo 從 null → 有值時主動 invalidate refetch
- 順手把 yaml-parser 對 FOREACH iterator relation 命名變體（「對每個 X」/「FOREACH X」）放行，graph-builder 早就支援，validate 卻擋掉

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

landing/app/mira/feed/page.tsx

@@ -216,17 +216,21 @@ async function fetchAllEntityNames(apiKey: string): Promise<Set<string>> {
   }
 }
 
-// Cache：每個 session 只 fetch 一次 entity list（autocomplete 用）
+// Cache：debounce 短 TTL（5s），同時 autocomplete 開啟時主動 refetch
+// 30s 太久：wiki_synthesis 後台跑出新 entity（如 Claude 自己命名的「李飛飛的視界之旅」）autocomplete 撈不到
 let cachedEntityNames: Set<string> | null = null;
 let cachedEntityFetchedAt = 0;
 async function getEntityNamesCached(apiKey: string): Promise<Set<string>> {
   const now = Date.now();
-  // 30s TTL — leo 持續寫貼文時新建的 entity 也能很快被 autocomplete 看到
-  if (cachedEntityNames && now - cachedEntityFetchedAt < 30_000) return cachedEntityNames;
+  if (cachedEntityNames && now - cachedEntityFetchedAt < 5_000) return cachedEntityNames;
   cachedEntityNames = await fetchAllEntityNames(apiKey);
   cachedEntityFetchedAt = now;
   return cachedEntityNames;
 }
+function invalidateEntityCache() {
+  cachedEntityNames = null;
+  cachedEntityFetchedAt = 0;
+}
 
 // 簡單 type 推測：《X》 → 書；http(s)://X → URL；其他 → 概念
 function guessEntityType(name: string): 'book' | 'url' | 'concept' {
@@ -664,10 +668,17 @@ function WikilinkAutocomplete({
   const [matchInfo, setMatchInfo] = useState<{ start: number; query: string } | null>(null);
   const [selectedIdx, setSelectedIdx] = useState(0);
 
-  // 載入 entity 清單（cached 30s）
+  // 載入 entity 清單（5s cache + 每次 `[[` 開啟時 refetch 保持新鮮）
   useEffect(() => {
     getEntityNamesCached(apiKey).then(set => setEntities(Array.from(set).sort()));
   }, [apiKey]);
+  // matchInfo 從 null → 有值 = 剛打開 autocomplete → 重抓
+  useEffect(() => {
+    if (!matchInfo) return;
+    invalidateEntityCache();
+    getEntityNamesCached(apiKey).then(set => setEntities(Array.from(set).sort()));
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [matchInfo !== null, apiKey]);
 
   // 監聽 textarea 變化 / cursor 移動 → 重算 matchInfo
   useEffect(() => {