fix(electron): resolve ELEC2-M1/L1/L2

- ELEC2-M1: MCP manager init failure resets initialized flag and
  retries with exponential backoff (1s-30s, max 8 attempts) - the
  stale flag previously disabled MCP silently for the whole run
- ELEC2-L1: window recreation (macOS activate) resets sync-before-quit
  state machine - stale requested=true + completed=false made the new
  window impossible to close
- ELEC2-L2: audio capture runtime degradation re-checks capturing
  before restarting the provider, eliminating ghost capture when
  stop() races with degradeToEndpoint

Author: Aparencia

client/electron/audioCapture.ts

@@ -219,6 +219,10 @@ export class AudioCapture {
       fallback: null,
     };
     try {
+      // ELEC2-L2: startWithKind 前二次校验——首次守卫后到此处存在 await 边界，
+      // stop() 可能已置 capturing=false；继续启动会产生幽灵采集（provider
+      // 已重启但无人会停止它）。降级结果以 capturing 最新状态为准
+      if (!this.capturing) return;
       await this.startWithKind('endpoint_loopback', this.boundWindow, this.boundSourceId);
     } catch (err) {
       logger.error('[AudioCapture] 降级到端点环回失败', err);

client/electron/mcpManager.ts

@@ -35,6 +35,11 @@ import {
 /** 单次请求超时（ms）——bridge 无响应时拒绝并清理 pending，防请求悬挂 */
 const REQUEST_TIMEOUT_MS = 30_000;
 
+// ELEC2-M1: init 失败后的指数退避重试参数（1s→2s→4s…封顶 30s，最多 8 次）
+const INIT_RETRY_BASE_MS = 1000;
+const INIT_RETRY_MAX_MS = 30_000;
+const INIT_RETRY_MAX_ATTEMPTS = 8;
+
 // ================================================================
 // 管理器
 // ================================================================
@@ -43,6 +48,9 @@ class McpManager {
   private bridge: ChildProcess | null = null;
   private initialized = false;
   private requestCounter = 0;
+  /** ELEC2-M1: init 重试计数与定时器（指数退避，环境故障自愈） */
+  private retryAttempts = 0;
+  private retryTimer: ReturnType<typeof setTimeout> | null = null;
   /** 待响应的请求回调 */
   private pending = new Map<string, {
     resolve: (value: unknown) => void;
@@ -124,9 +132,33 @@ class McpManager {
     } catch (err) {
       logger.error('[MCP] Manager init failed', err);
       this.killBridge();
+      // ELEC2-M1: 重置 initialized 并指数退避重试——原实现保留 true 导致
+      // MCP 功能本次运行永久静默禁用（bridge 故障/环境变量缺失后无自愈机会）
+      this.initialized = false;
+      this.scheduleRetryInit();
     }
   }
 
+  /**
+   * ELEC2-M1: 指数退避重试 init（1s→2s→4s…封顶 30s，最多 8 次）
+   * 环境类故障（PATH 缺失、bridge 编译产物未就绪）通常可自愈
+   */
+  private scheduleRetryInit(): void {
+    if (this.retryTimer) return; // 已有重试计划
+    if (this.retryAttempts >= INIT_RETRY_MAX_ATTEMPTS) {
+      logger.error('[MCP] Init retry attempts exhausted, giving up');
+      return;
+    }
+    const delay = Math.min(INIT_RETRY_BASE_MS * 2 ** this.retryAttempts, INIT_RETRY_MAX_MS);
+    this.retryAttempts += 1;
+    this.retryTimer = setTimeout(() => {
+      this.retryTimer = null;
+      if (this.initialized) return; // 已成功，无需重试
+      logger.info(`[MCP] Retrying init (attempt ${this.retryAttempts}/${INIT_RETRY_MAX_ATTEMPTS})...`);
+      void this.init().catch(() => {});
+    }, delay);
+  }
+
   /**
    * 列出指定 server 的所有可用工具
    */
@@ -173,6 +205,12 @@ class McpManager {
   async shutdown(): Promise<void> {
     logger.info('[MCP] Shutting down MCP Manager...');
 
+    // ELEC2-M1: 取消未执行的重试定时器（退出时不再自愈）
+    if (this.retryTimer) {
+      clearTimeout(this.retryTimer);
+      this.retryTimer = null;
+    }
+
     if (this.bridge) {
       try {
         // 给 bridge 1 秒时间优雅关闭（避免阻塞退出）

client/electron/windowManager.ts

@@ -78,6 +78,12 @@ export function createMainWindow(
   isQuittingRef: { value: boolean },
   onQuit: () => void,
 ): BrowserWindow {
+  // ELEC2-L1: 窗口创建（含 macOS activate 重建）时重置退出前同步状态机——
+  // 旧状态残留 requested=true 且 completed=false 时，新窗口 close 永远
+  // preventDefault 无法关闭（同步事件只在旧窗口的 webContents 上发送过）
+  syncBeforeQuitRequested = false;
+  syncBeforeQuitCompleted = false;
+
   const win = new BrowserWindow({
     width: WINDOW_DEFAULT_WIDTH,
     height: WINDOW_DEFAULT_HEIGHT,