fix: restore AI suggestion filter by selection, cache PromptTemplateManager

Cache PromptTemplateManager in ref to prevent new instance per
render. Filter: show only Rearrange/favorites when MIDI item
selected, all presets otherwise. Root cause of 'suggestion added
at top' was stale array reference from new instance every render.

app/static/js/app.jsx

@@ -7294,6 +7294,7 @@ const App = () => {
   const [showAiTypeahead, setShowAiTypeahead] = useState(false);
   const [showAISuggestions, setShowAISuggestions] = useState(true);
   const [showAIActionLog, setShowAIActionLog] = useState(false);
+  const aiPromptMgrRef = useRef(null);
   const [selectedProviderId, setSelectedProviderId] = useState('');
   const [exportSettings, setExportSettings] = useState({
     sampleRate: '44100',
@@ -16176,8 +16177,11 @@ const App = () => {
       if (panelId === 'ai') {
         const selMidiInfo = getSelectedMidiItemInfo();
         const hasSelItem = !!selMidiInfo;
-        const promptMgr = window.PromptTemplateManager ? new window.PromptTemplateManager() : null;
-        const suggestions = promptMgr ? promptMgr.presets : [];
+        if (window.PromptTemplateManager && !aiPromptMgrRef.current) {
+          aiPromptMgrRef.current = new window.PromptTemplateManager();
+        }
+        const promptMgr = aiPromptMgrRef.current;
+        const suggestions = promptMgr ? (hasSelItem ? promptMgr.presets.filter(function(p) { return p.category === 'Rearrange / Variation' || p.is_favorite; }) : promptMgr.presets) : [];
         const handleApplySuggestion = (preset) => {
           if (hasSelItem) {
             setAiPrompt(`Rearrange this melody line in ${preset.name} style`);

wiki.md

@@ -700,3 +700,9 @@
 - **Các file ảnh hưởng:** `app/static/js/app.jsx`
 - **Ghi chú/Test (nếu có):** `npm run build` — build passes.
 ---
+
+### [2026-07-29 10:12] Task: Restore AI suggestion filter by selection + fix stale instance
+- **Tóm tắt thay đổi:** Restore filter: khi chọn MIDI item chỉ hiện Rearrange/favorites, không chọn thì hiện tất cả. Fix gốc: cache PromptTemplateManager qua `aiPromptMgrRef` thay vì `new` mỗi render — tránh thay đổi array reference gây re-render suggestion list.
+- **Các file ảnh hưởng:** `app/static/js/app.jsx`
+- **Ghi chú/Test (nếu có):** `npm run build` — build passes.
+---