fix(mira): reply @mira indicator + RAG match 寬鬆化

leo 試用反饋：

bug：reply 中 @mira 「看起來無效」
- 真正 root cause: trigger 確實 fire，但 thinking indicator 沒亮起 → leo 沒看到回應
  以為失敗（其實 mira 後台跑 30s+ 才回）
- 修：MiraTriggerContext 把 thinking trigger 抽成 context callback
  PostComposer / PostEditor / BlockEditor / ReplyLine 五個 @mira 觸發點
  都呼叫 triggerThinking?.(docPageName) 啟動 5s polling

bug：RAG 抓不到 entity（leo 寫《李飛飛的視界之旅》沒被識別）
- 之前只看 type=index-entry，且嚴格 substring。新建 wiki 還沒 index-entry
  時就漏；entity 名稱跟貼文文字稍微不同也漏
- 修 fetchRelevantWikiContext：
  - 平行撈 index-entry + wiki-page 兩種，合併 entity set
  - 雙向匹配：entity 完整 substring postContent（嚴格） OR
    entity 內 3+ 字片段在 postContent 出現（寬鬆，中文友善）
  - top 5（從 3 增加），給 mira 更多上下文

landing/app/mira/feed/page.tsx

@@ -3,10 +3,17 @@
 // Mira 河道 — 社群貼文式設計（FB / X 風格）
 // SDD: polaris/mira/.agents/specs/mira-app/design.md §5.3
 
-import { useEffect, useState, useCallback, useRef, useMemo } from 'react';
+import { useEffect, useState, useCallback, useRef, useMemo, createContext, useContext } from 'react';
 import { MarkdownView } from '../_shared/markdown';
 import '../mira.css';
 
+// Context：把「mira 已觸發要顯示 thinking + 啟動 polling」設定 callback 傳到深層 reply / edit 元件
+// 不用 prop drill。對應 P0 #5b bug fix（leo 反饋：reply 中 @mira 沒看到 indicator → 以為失敗）
+const MiraTriggerContext = createContext<((pageName: string) => void) | null>(null);
+function useMiraTrigger() {
+  return useContext(MiraTriggerContext);
+}
+
 const API_BASE = process.env.NEXT_PUBLIC_API_BASE ?? 'https://cypher.arcrun.dev';
 const KBDB_BASE = 'https://kbdb.finally.click';
 const KBDB_INGEST = 'https://kbdb-ingest.arcrun.dev';
@@ -101,26 +108,30 @@ export default function MiraPage() {
     return () => { cancelled = true; };
   }, []);
 
+  // 把 thinking trigger 抽成共用 callback（PostComposer 跟所有 reply / edit 子元件用同一份）
+  const triggerThinking = useCallback((pageName: string) => {
+    setAiThinking(prev => new Set(prev).add(pageName));
+    // 90 秒後 hard timeout（Mira 思考 + KBDB write 通常 10-45 秒，給寬限）
+    // 卡片內 useEffect 偵測 AI reply 真的進來會主動呼叫 onAiResponded 清掉
+    setTimeout(() => {
+      setAiThinking(prev => {
+        if (!prev.has(pageName)) return prev;
+        const n = new Set(prev);
+        n.delete(pageName);
+        return n;
+      });
+    }, 90000);
+  }, []);
+
   return (
+    <MiraTriggerContext.Provider value={triggerThinking}>
     <div className="mira-app">
       <div className="mira-content">
         {me && (
           <PostComposer
             me={me}
             onPosted={reload}
-            onAiTriggered={(pageName) => {
-              setAiThinking(prev => new Set(prev).add(pageName));
-              // 90 秒後 hard timeout（Mira 思考 + KBDB write 通常 10-45 秒，給寬限）
-              // 卡片內 useEffect 偵測 AI reply 真的進來會主動呼叫 onAiResponded 清掉
-              setTimeout(() => {
-                setAiThinking(prev => {
-                  if (!prev.has(pageName)) return prev;
-                  const n = new Set(prev);
-                  n.delete(pageName);
-                  return n;
-                });
-              }, 90000);
-            }}
+            onAiTriggered={triggerThinking}
           />
         )}
 
@@ -153,6 +164,7 @@ export default function MiraPage() {
         )}
       </div>
     </div>
+    </MiraTriggerContext.Provider>
   );
 }
 
@@ -165,30 +177,61 @@ function hasMiraMention(text: string): boolean {
 }
 
 // 撈相關 wiki context 給 mira reply 用（簡單 RAG）
-// 策略：拿全部 index-entry blocks → 用 entity 名稱 keyword match against post content
-// → 取 top 3 把整篇 markdown 餵進 prompt（每篇通常 < 1KB，3 篇還在 token 預算內）
+// 策略：拿全部 index-entry + wiki-page，雙向 substring match against post content
+// → 取 top 5 餵進 prompt
 async function fetchRelevantWikiContext(apiKey: string, postContent: string): Promise<string> {
   try {
-    const res = await fetch(`${KBDB_BASE}/blocks?type=index-entry&limit=200`, {
-      headers: { Authorization: `Bearer ${apiKey}` },
-    });
-    if (!res.ok) return '';
-    const data = await res.json() as { blocks?: Array<{ id: string; page_name: string | null; content: string }> };
-    const all = data.blocks ?? [];
-    if (all.length === 0) return '';
+    const headers = { Authorization: `Bearer ${apiKey}` };
+    // 平行撈 index-entry（含 markdown 摘要）跟 wiki-page（content 是 entity 名稱）
+    const [idxRes, pageRes] = await Promise.all([
+      fetch(`${KBDB_BASE}/blocks?type=index-entry&limit=200`, { headers }),
+      fetch(`${KBDB_BASE}/blocks?type=wiki-page&source=ai-canon-wiki&limit=200`, { headers }),
+    ]);
+    type B = { id: string; page_name: string | null; content: string };
+    const idxData = idxRes.ok ? await idxRes.json() as { blocks?: B[] } : { blocks: [] };
+    const pageData = pageRes.ok ? await pageRes.json() as { blocks?: B[] } : { blocks: [] };
+
+    // 收集 unique entity 名稱（從 index-entry page_name 跟 wiki-page content）+ 對應 markdown
+    const entityMap = new Map<string, string>(); // entity name -> 顯示用 markdown context
+    for (const b of (idxData.blocks ?? [])) {
+      const entity = (b.page_name ?? '').replace(/^index-/, '').trim();
+      if (entity && !entityMap.has(entity)) entityMap.set(entity, b.content);
+    }
+    for (const b of (pageData.blocks ?? [])) {
+      const entity = (b.content ?? '').trim();
+      if (entity && !entityMap.has(entity)) {
+        // wiki-page content 只有 entity 名稱，沒摘要 — 給最簡 placeholder
+        entityMap.set(entity, `（已建 wiki-page，但尚無 index-entry 摘要）`);
+      }
+    }
+    if (entityMap.size === 0) return '';
+
+    // 雙向 substring match：
+    //   - entity 名稱 substring of postContent，或
+    //   - postContent 中任 4+ 字 sliding window substring of entity（中文場景容忍）
     const lower = postContent.toLowerCase();
-    // 評分：page_name 剝 `index-` prefix = entity 名稱，看 postContent 是否含
-    const scored = all
-      .map(b => {
-        const entity = (b.page_name ?? '').replace(/^index-/, '').trim();
-        const score = entity && lower.includes(entity.toLowerCase()) ? entity.length : 0;
-        return { entity, content: b.content, score };
-      })
-      .filter(x => x.score > 0)
-      .sort((a, b) => b.score - a.score)
-      .slice(0, 3);
-    if (scored.length === 0) return '';
-    return scored.map(s => `### entity: ${s.entity}\n${s.content}`).join('\n\n');
+    const scored: Array<{ entity: string; content: string; score: number }> = [];
+    for (const [entity, content] of entityMap) {
+      const e = entity.toLowerCase();
+      let score = 0;
+      // 直接 substring（嚴格）
+      if (lower.includes(e)) score = e.length * 2;
+      // 較寬鬆：entity 內 ≥ 3 字片段在 postContent 出現
+      else if (e.length >= 3) {
+        for (let i = 0; i + 3 <= e.length; i++) {
+          const frag = e.slice(i, i + Math.min(4, e.length - i));
+          if (frag.length >= 3 && lower.includes(frag)) {
+            score = Math.max(score, frag.length);
+            break;
+          }
+        }
+      }
+      if (score > 0) scored.push({ entity, content, score });
+    }
+    scored.sort((a, b) => b.score - a.score);
+    const top = scored.slice(0, 5);
+    if (top.length === 0) return '';
+    return top.map(s => `### entity: ${s.entity}\n${s.content}`).join('\n\n');
   } catch (e) {
     console.warn('[fetchRelevantWikiContext] failed', e);
     return '';
@@ -978,6 +1021,7 @@ function PostEditor({
   const [draft, setDraft] = useState(initial);
   const [saving, setSaving] = useState(false);
   const [err, setErr] = useState<string | null>(null);
+  const triggerThinking = useMiraTrigger();
 
   const save = async () => {
     if (saving) return;
@@ -1031,6 +1075,7 @@ function PostEditor({
           void triggerAiReply({
             apiKey, postContent: trimmed, parentBlockId: firstId, pageName,
           });
+          triggerThinking?.(pageName);
         }
       }
     } catch (e) {
@@ -1107,6 +1152,7 @@ function BlockLine({
   const [draft, setDraft] = useState(block.content ?? '');
   const [saving, setSaving] = useState(false);
   const [err, setErr] = useState<string | null>(null);
+  const triggerThinking = useMiraTrigger();
 
   const startEdit = () => { setDraft(block.content ?? ''); setMode('edit'); setErr(null); };
   const startReply = () => { setDraft(''); setMode('reply'); setErr(null); };
@@ -1130,6 +1176,7 @@ function BlockLine({
         void triggerAiReply({
           apiKey, postContent: draft, parentBlockId: block.id, pageName: docPageName,
         });
+        triggerThinking?.(docPageName);
       }
       setMode('view');
     } catch (e) { setErr(e instanceof Error ? e.message : String(e)); }
@@ -1166,6 +1213,7 @@ function BlockLine({
         void triggerAiReply({
           apiKey, postContent: trimmed, parentBlockId: data.data.id, pageName: docPageName,
         });
+        triggerThinking?.(docPageName);
       }
       setMode('view'); setDraft('');
     } catch (e) { setErr(e instanceof Error ? e.message : String(e)); }
@@ -1235,6 +1283,7 @@ function ReplyLine({
   const [saving, setSaving] = useState(false);
   const [err, setErr] = useState<string | null>(null);
   const isAI = reply.source?.startsWith('ai-') ?? false;
+  const triggerThinking = useMiraTrigger();
 
   const startEdit = () => { setDraft(reply.content ?? ''); setMode('edit'); setErr(null); };
   const startReply = () => { setDraft(''); setMode('reply'); setErr(null); };
@@ -1257,6 +1306,7 @@ function ReplyLine({
         void triggerAiReply({
           apiKey, postContent: draft, parentBlockId: reply.id, pageName: docPageName,
         });
+        triggerThinking?.(docPageName);
       }
       setMode('view');
     } catch (e) { setErr(e instanceof Error ? e.message : String(e)); }
@@ -1293,6 +1343,7 @@ function ReplyLine({
         void triggerAiReply({
           apiKey, postContent: trimmed, parentBlockId: data.data.id, pageName: docPageName,
         });
+        triggerThinking?.(docPageName);
       }
       setMode('view'); setDraft('');
     } catch (e) { setErr(e instanceof Error ? e.message : String(e)); }