Rework shell exit state

app/src/main/java/io/xpipe/app/process/ShellControl.java

@@ -22,6 +22,8 @@ public interface ShellControl extends ProcessControl {
 
     void setUser(String user);
 
+    boolean isExiting();
+
     boolean isInitializing();
 
     void setDumbOpen(ShellOpenFunction openFunction);

app/src/main/java/io/xpipe/app/process/WrapperShellControl.java

@@ -216,6 +216,11 @@ public class WrapperShellControl implements ShellControl {
         parent.setUser(user);
     }
 
+    @Override
+    public boolean isExiting() {
+        return parent.isExiting();
+    }
+
     @Override
     public boolean isInitializing() {
         return parent.isInitializing();