feat(classroom): P0-7 识别统计条（引擎徽标+帧数+句数+VAD状态）

Author: Aparencia

client/src/features/classroom/components/RecognitionStatsBar.test.tsx

@@ -0,0 +1,98 @@
+/**
+ * RecognitionStatsBar 渲染测试（P0-7）
+ *
+ * @ai-context: 锁定识别统计条展示契约：引擎徽标三态（本地流式 > 本地按段 >
+ * 云端）、关键帧/转写计数、VAD 语音状态（语音中/静默/已停止）。
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { RecognitionStatsBar } from './RecognitionStatsBar';
+import type { VADStats } from '@/lib/capture/vadMarker';
+
+function makeVad(lastVoiceTimestamp: number): VADStats {
+  return {
+    currentThreshold: 0.008,
+    segmentCount: 0,
+    lastVoiceTimestamp,
+    calibrated: true,
+    processedChunks: 0,
+  };
+}
+
+describe('RecognitionStatsBar', () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date('2026-08-16T10:00:00Z'));
+  });
+  afterEach(() => vi.useRealTimers());
+
+  it('本地流式引擎徽标 + 帧数/句数统计', () => {
+    render(
+      <RecognitionStatsBar
+        status="capturing"
+        keyframeCount={12}
+        transcribedCount={34}
+        vadStats={makeVad(0)}
+        streamingAsrActive
+        localAsrReady
+      />,
+    );
+    expect(screen.getByText('本地流式')).toBeTruthy();
+    expect(screen.getByText('12')).toBeTruthy();
+    expect(screen.getByText('34')).toBeTruthy();
+  });
+
+  it('云端转写引擎徽标（本地不可用且非流式）', () => {
+    render(
+      <RecognitionStatsBar
+        status="capturing"
+        keyframeCount={0}
+        transcribedCount={0}
+        vadStats={null}
+        streamingAsrActive={false}
+        localAsrReady={false}
+      />,
+    );
+    expect(screen.getByText('云端转写')).toBeTruthy();
+    expect(screen.getByText('—')).toBeTruthy();
+  });
+
+  it('VAD 语音状态：最近 2s 有语音 → 语音中；否则静默；停止态 → 已停止', () => {
+    const now = Date.now();
+    const { rerender } = render(
+      <RecognitionStatsBar
+        status="capturing"
+        keyframeCount={0}
+        transcribedCount={0}
+        vadStats={makeVad(now - 500)}
+        streamingAsrActive={false}
+        localAsrReady={false}
+      />,
+    );
+    expect(screen.getByText('语音中')).toBeTruthy();
+
+    rerender(
+      <RecognitionStatsBar
+        status="capturing"
+        keyframeCount={0}
+        transcribedCount={0}
+        vadStats={makeVad(now - 10_000)}
+        streamingAsrActive={false}
+        localAsrReady={false}
+      />,
+    );
+    expect(screen.getByText('静默')).toBeTruthy();
+
+    rerender(
+      <RecognitionStatsBar
+        status="idle"
+        keyframeCount={0}
+        transcribedCount={0}
+        vadStats={makeVad(now - 500)}
+        streamingAsrActive={false}
+        localAsrReady={false}
+      />,
+    );
+    expect(screen.getByText('已停止')).toBeTruthy();
+  });
+});

client/src/features/classroom/components/RecognitionStatsBar.tsx

@@ -0,0 +1,74 @@
+/**
+ * RecognitionStatsBar — 识别统计条（P0-7）
+ *
+ * @ai-context: 识别过程可见性（UX-F 基础）：会话中实时展示识别引擎徽标、
+ * 已捕捉关键帧数、已转写句数、VAD 语音状态。数据全部来自既有会话状态
+ * （smartBundle.keyframes / transcribedCount / vadStats），纯展示零逻辑，
+ * 不引入新订阅。
+ * @ai-context EN: Live recognition status bar: engine badge (local streaming /
+ * local segment / cloud), captured keyframes, transcribed segments, and VAD
+ * voice state. Pure presentation over existing session state.
+ */
+import { Cpu, Camera, Mic, Activity } from 'lucide-react';
+import type { SessionStatus } from '@/lib/capture';
+import type { VADStats } from '@/lib/capture/vadMarker';
+
+interface RecognitionStatsBarProps {
+  status: SessionStatus;
+  keyframeCount: number;
+  transcribedCount: number;
+  vadStats: VADStats | null;
+  /** 真流式 ASR 激活（smart 路径 Zipformer 在线识别） */
+  streamingAsrActive: boolean;
+  /** 本地 ASR 引擎就绪（否则转写走云端） */
+  localAsrReady: boolean;
+}
+
+/** 引擎徽标文案与配色（本地流式 > 本地按段 > 云端） */
+function engineBadge(streamingAsrActive: boolean, localAsrReady: boolean): { label: string; cls: string } {
+  if (streamingAsrActive) {
+    return { label: '本地流式', cls: 'text-emerald-600 bg-emerald-500/10' };
+  }
+  if (localAsrReady) {
+    return { label: '本地按段', cls: 'text-emerald-600 bg-emerald-500/10' };
+  }
+  return { label: '云端转写', cls: 'text-accent-600 bg-accent-500/10' };
+}
+
+/** VAD 语音状态：最近 2s 内有语音活动视为「语音中」（vadStats 5s 粒度） */
+function vadVoiceState(vadStats: VADStats | null): { label: string; speaking: boolean } {
+  if (!vadStats) return { label: '—', speaking: false };
+  const recent = Date.now() - vadStats.lastVoiceTimestamp < 2000;
+  return recent ? { label: '语音中', speaking: true } : { label: '静默', speaking: false };
+}
+
+export function RecognitionStatsBar({
+  status, keyframeCount, transcribedCount, vadStats, streamingAsrActive, localAsrReady,
+}: RecognitionStatsBarProps) {
+  const engine = engineBadge(streamingAsrActive, localAsrReady);
+  const voice = vadVoiceState(vadStats);
+
+  return (
+    <div className="mx-4 mt-2 flex items-center gap-3 px-3 py-1.5 rounded-kb-md bg-bg-elevated/40 border border-border/20 text-[11px] text-text-tertiary flex-wrap">
+      <span className="flex items-center gap-1">
+        <Cpu className="w-3 h-3" strokeWidth={1.5} />
+        识别引擎
+        <span className={`px-1.5 py-0.5 rounded-kb-sm font-medium ${engine.cls}`}>{engine.label}</span>
+      </span>
+      <span className="flex items-center gap-1">
+        <Camera className="w-3 h-3" strokeWidth={1.5} />
+        已捕捉 <strong className="text-text-secondary">{keyframeCount}</strong> 帧
+      </span>
+      <span className="flex items-center gap-1">
+        <Mic className="w-3 h-3" strokeWidth={1.5} />
+        已转写 <strong className="text-text-secondary">{transcribedCount}</strong> 句
+      </span>
+      <span className="flex items-center gap-1">
+        <Activity className={`w-3 h-3 ${voice.speaking ? 'text-emerald-500' : ''}`} strokeWidth={1.5} />
+        {status === 'capturing' ? voice.label : '已停止'}
+      </span>
+    </div>
+  );
+}
+
+export default RecognitionStatsBar;

client/src/features/classroom/components/SessionContentView.tsx

@@ -19,6 +19,8 @@ import { useClassroomCapture } from '../hooks/useClassroomCapture';
 import { SegmentList } from './SegmentList';
 import { UnifiedTimeline } from './UnifiedTimeline';
 import { ClassroomStatusBanners } from './ClassroomStatusBanners';
+import { RecognitionStatsBar } from './RecognitionStatsBar';
+import { isLocalAsrReady } from '../utils/asrTranscriber';
 import { AnalysisPreview } from '@/features/notes/components/AnalysisPreview';
 import { VideoRecordPanel } from '@/features/notes/components/VideoRecordPanel';
 import SessionQAPanel from './SessionQAPanel';
@@ -84,6 +86,15 @@ export function SessionContentView({ capture, onOpenNoteDialog }: SessionContent
                 audioHealth={capture.audioHealth}
                 vadStats={capture.vadStats}
               />
+              {/* P0-7 识别统计条：引擎徽标 / 帧数 / 句数 / VAD 语音状态 */}
+              <RecognitionStatsBar
+                status={capture.status}
+                keyframeCount={capture.smartBundle?.keyframes?.length ?? 0}
+                transcribedCount={capture.transcribedCount}
+                vadStats={capture.vadStats}
+                streamingAsrActive={capture.streamingAsrActive}
+                localAsrReady={isLocalAsrReady()}
+              />
               {/* M2 自动锚点以时间线行展示（autoAnchors 独立数据源） */}
               <UnifiedTimeline
                 bundle={capture.smartBundle}