fix(mail): replace os.Exit with graceful shutdown in mail watch

shortcuts/mail/mail_watch.go

@@ -424,6 +424,9 @@ var MailWatch = common.Shortcut{
 			larkws.WithLogger(sdkLogger),
 		)
 
+		watchCtx, cancelWatch := context.WithCancel(ctx)
+		defer cancelWatch()
+
 		sigCh := make(chan os.Signal, 1)
 		signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
 		go func() {
@@ -433,26 +436,34 @@ var MailWatch = common.Shortcut{
 				}
 			}()
 			<-sigCh
+			signal.Stop(sigCh)
 			info(fmt.Sprintf("\nShutting down... (received %d events)", eventCount))
 			info("Unsubscribing mailbox events...")
 			if unsubErr := unsubscribe(); unsubErr != nil {
 				fmt.Fprintf(errOut, "Warning: unsubscribe failed: %v\n", unsubErr)
 			} else {
 				info("Mailbox unsubscribed.")
 			}
-			signal.Stop(sigCh)
-			os.Exit(0)
+			cancelWatch()
 		}()
 
 		info("Connected. Waiting for mail events... (Ctrl+C to stop)")
-		if err := cli.Start(ctx); err != nil {
-			unsubscribe() //nolint:errcheck // best-effort cleanup
-			return output.ErrNetwork("WebSocket connection failed: %v", err)
+		if err := cli.Start(watchCtx); err != nil {
+			return handleMailWatchStartError(err, watchCtx, unsubscribe)
 		}
 		return nil
 	},
 }
 
+func handleMailWatchStartError(err error, watchCtx context.Context, unsubscribe func() error) error {
+	if watchCtx.Err() != nil {
+		// Graceful shutdown via signal cancellation; not an error.
+		return nil
+	}
+	unsubscribe() //nolint:errcheck // best-effort cleanup
+	return output.ErrNetwork("WebSocket connection failed: %v", err)
+}
+
 // extractMailEventBody extracts the event body from the Lark event envelope.
 func extractMailEventBody(data map[string]interface{}) map[string]interface{} {
 	// V2 envelope: { header: {...}, event: { mail_address, message_id, ... } }

shortcuts/mail/mail_watch_test.go

@@ -539,6 +539,40 @@ func TestWrapWatchSubscribeErrorExitError(t *testing.T) {
 	}
 }
 
+func TestHandleMailWatchStartErrorGracefulShutdownSkipsCleanup(t *testing.T) {
+	watchCtx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	unsubscribeCalled := false
+	err := handleMailWatchStartError(assertErr("context canceled"), watchCtx, func() error {
+		unsubscribeCalled = true
+		return nil
+	})
+	if err != nil {
+		t.Fatalf("expected nil error, got %v", err)
+	}
+	if unsubscribeCalled {
+		t.Fatal("unsubscribe should not be called for graceful shutdown")
+	}
+}
+
+func TestHandleMailWatchStartErrorNetworkFailureCleansUp(t *testing.T) {
+	unsubscribeCalled := false
+	err := handleMailWatchStartError(assertErr("boom"), context.Background(), func() error {
+		unsubscribeCalled = true
+		return nil
+	})
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	if !unsubscribeCalled {
+		t.Fatal("expected unsubscribe to be called for startup failure")
+	}
+	if !strings.Contains(err.Error(), "WebSocket connection failed: boom") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
 // --- watchFetchFormat ---
 
 func TestWatchFetchFormat(t *testing.T) {