Look for $SHLVL when determining whether in a terminal

src/mads/environ/in_out.py

@@ -16,17 +16,22 @@ class InOut(BaseSettings):
 
     term: str | None = None
     force_terminal: bool | None = None
+    shlvl: int | None = None
 
     @computed_field
     def is_terminal(self) -> bool:
         if self.force_terminal is not None:
             return self.force_terminal
-        return self.is_atty
+        return bool(self.is_atty or self.is_subshell)
 
     @computed_field
     def is_atty(self) -> bool:
         return sys.stdout.isatty()
 
+    @computed_field
+    def is_subshell(self) -> bool:
+        return self.shlvl is not None and self.shlvl > 1
+
     @computed_field
     def is_interactive(self) -> bool:
         return self.is_atty and not self.is_dumb