feat(pet): Mochi celebrates when tasks are completed

1.8s animation: tail wag (6 segments), ear wiggle (L/R), eye smile,
cheek blush, body bounce. Uses Cubism coreModel.setParameterValueById.
Triggered by detecting task.completed transition from false→true.

frontend/src/App.tsx

@@ -29,6 +29,7 @@ export default function App() {
     startRecording,
     stopRecording,
     tasks,
+    celebrateTrigger,
     addTask,
   } = useConversation();
 
@@ -111,6 +112,7 @@ export default function App() {
         onReady={() => setLive2dReady(true)}
         isSpeaking={isKiraSpeaking}
         outfit={currentOutfit}
+        celebrateTrigger={celebrateTrigger}
       />
 
       <Particles type={currentScene.particles ?? 'none'} />

frontend/src/components/Live2DStage.tsx

@@ -5,6 +5,7 @@ interface Props {
   onReady?: () => void;
   isSpeaking?: boolean;
   outfit?: string;
+  celebrateTrigger?: number;
 }
 
 /**
@@ -48,9 +49,10 @@ function positionCat(cat: any) {
   cat.position.set(r.left + r.width / 2, r.top + r.height / 2 + 10);
 }
 
-export default function Live2DStage({ onKiraReady, onReady, outfit }: Props) {
+export default function Live2DStage({ onKiraReady, onReady, outfit, celebrateTrigger }: Props) {
   const canvasRef = useRef<HTMLCanvasElement>(null);
   const kiraModelRef = useRef<any>(null);
+  const catModelRef = useRef<any>(null);
   const pixiAppRef = useRef<any>(null);
 
   useEffect(() => {
@@ -119,6 +121,7 @@ export default function Live2DStage({ onKiraReady, onReady, outfit }: Props) {
           positionCat(catModel);
           (catModel as any).isInteractive = () => false;
           app.stage.addChild(catModel as any);
+          catModelRef.current = catModel;
 
           try { catModel.motion('Idle'); } catch {}
         } catch (e) {
@@ -213,6 +216,105 @@ export default function Live2DStage({ onKiraReady, onReady, outfit }: Props) {
     return () => { cancelled = true; };
   }, [outfit]);
 
+  // Celebration animation effect
+  useEffect(() => {
+    const cat = catModelRef.current;
+    if (!cat || celebrateTrigger === undefined || celebrateTrigger === 0) return;
+
+    const coreModel = cat.internalModel?.coreModel;
+    if (!coreModel) return;
+
+    const PARAMS = {
+      tail0: 'Param_Angle_Rotation2',
+      tail1: 'Param_Angle_Rotation3',
+      tail2: 'Param_Angle_Rotation4',
+      tail3: 'Param_Angle_Rotation5',
+      tail4: 'Param_Angle_Rotation6',
+      tail5: 'Param_Angle_Rotation7',
+      earL0: 'Param_Angle_Rotation10',
+      earL1: 'Param_Angle_Rotation11',
+      earR0: 'Param_Angle_Rotation12',
+      earR1: 'Param_Angle_Rotation13',
+      cheek: 'ParamCheek',
+      eyeSmileL: 'ParamEyeLSmile',
+      eyeSmileR: 'ParamEyeRSmile',
+      bodyX: 'ParamBodyAngleX',
+      bodyY: 'ParamBodyAngleY',
+      mouth: 'ParamMouthOpenY',
+    };
+
+    const getParamIndex = (id: string) => {
+      try { return coreModel.getParameterIndex(id); } catch { return -1; }
+    };
+
+    const setParam = (id: string, value: number) => {
+      const idx = getParamIndex(id);
+      if (idx >= 0) coreModel.setParameterValueById(id, value);
+    };
+
+    const saveBase = (id: string): number => {
+      const idx = getParamIndex(id);
+      return idx >= 0 ? coreModel.getParameterValueById(id) : 0;
+    };
+
+    // Save base values
+    const base: Record<string, number> = {};
+    for (const param of Object.values(PARAMS)) {
+      base[param] = saveBase(param);
+    }
+
+    let start = 0;
+    const DURATION = 1800; // ms
+    let animId: number;
+
+    const animate = (ts: number) => {
+      if (!start) start = ts;
+      const elapsed = ts - start;
+      const t = Math.min(elapsed / DURATION, 1);
+
+      // Bounce curve (3 bounces that decay)
+      const bounce = Math.sin(t * Math.PI * 6) * (1 - t) * 15;
+      const squish = 1 + Math.sin(t * Math.PI * 6) * (1 - t) * 0.03;
+
+      // Tail wag (all segments)
+      const tailWag = Math.sin(t * Math.PI * 8) * (1 - t) * 0.7;
+      setParam(PARAMS.tail0, base[PARAMS.tail0] + tailWag);
+      setParam(PARAMS.tail1, base[PARAMS.tail1] + tailWag * 0.8);
+      setParam(PARAMS.tail2, base[PARAMS.tail2] + tailWag * 0.6);
+      setParam(PARAMS.tail3, base[PARAMS.tail3] + tailWag * 0.4);
+      setParam(PARAMS.tail4, base[PARAMS.tail4] + tailWag * 0.3);
+      setParam(PARAMS.tail5, base[PARAMS.tail5] + tailWag * 0.2);
+
+      // Ear wiggle
+      const earWig = Math.sin(t * Math.PI * 10) * (1 - t) * 0.5;
+      setParam(PARAMS.earL0, base[PARAMS.earL0] + earWig);
+      setParam(PARAMS.earL1, base[PARAMS.earL1] + earWig * 0.6);
+      setParam(PARAMS.earR0, base[PARAMS.earR0] - earWig);
+      setParam(PARAMS.earR1, base[PARAMS.earR1] - earWig * 0.6);
+
+      // Happy face: eye smile + cheek blush + open mouth
+      const faceEase = Math.sin(t * Math.PI) ; // peaks at t=0.5
+      setParam(PARAMS.eyeSmileL, Math.max(base[PARAMS.eyeSmileL], faceEase));
+      setParam(PARAMS.eyeSmileR, Math.max(base[PARAMS.eyeSmileR], faceEase));
+      setParam(PARAMS.cheek, Math.max(base[PARAMS.cheek], faceEase * 0.8));
+      setParam(PARAMS.mouth, Math.max(base[PARAMS.mouth], faceEase * 0.4));
+
+      // Body bounce
+      setParam(PARAMS.bodyY, base[PARAMS.bodyY] + bounce);
+      cat.scale.set(cat.scale.x / (cat.scale.x || 1) * squish * (cat.scale.x || 1));
+
+      if (t < 1) {
+        animId = requestAnimationFrame(animate);
+      } else {
+        // Reset scale
+        positionCat(cat);
+      }
+    };
+
+    animId = requestAnimationFrame(animate);
+    return () => cancelAnimationFrame(animId);
+  }, [celebrateTrigger]);
+
   return (
     <canvas
       ref={canvasRef}

frontend/src/hooks/useConversation.ts

@@ -70,6 +70,7 @@ export function useConversation() {
   const [loadingPrefs, setLoadingPrefs] = useState(true);
   const [micError, setMicError] = useState<string | null>(null);
   const [tasks, setTasks] = useState<Task[]>([]);
+  const [celebrateTrigger, setCelebrateTrigger] = useState(0);
 
   const wsRef = useRef<WebSocket | null>(null);
   const streamRef = useRef<MediaStream | null>(null);
@@ -168,7 +169,17 @@ export function useConversation() {
         break;
 
       case 'tasks':
-        if (msg.tasks) setTasks(msg.tasks);
+        if (msg.tasks) {
+          setTasks((prev) => {
+            // Detect newly completed tasks
+            const prevMap = new Map(prev.map(t => [t.id, t.completed]));
+            const newCompleted = msg.tasks.filter((t: Task) => t.completed && !prevMap.get(t.id));
+            if (newCompleted.length > 0) {
+              setCelebrateTrigger(c => c + 1);
+            }
+            return msg.tasks;
+          });
+        }
         break;
     }
   }, []);
@@ -331,6 +342,7 @@ export function useConversation() {
     startRecording,
     stopRecording,
     tasks,
+    celebrateTrigger,
     addTask: (text: string) => {
       if (!text.trim() || !wsRef.current || wsRef.current.readyState !== WebSocket.OPEN) return;
       wsRef.current.send(JSON.stringify({ type: 'add_task', text: text.trim() }));