fix: harden legacy/tui3 non-tty flows and shutdown stability

src/utils/password_prompt.py

@@ -142,6 +142,8 @@ def prompt_new_password(max_retries: int | None = None) -> str:
             print(colored("\nOperation cancelled by user.", "yellow"))
             logging.info("Password prompt interrupted by user.")
             raise PasswordPromptError("Operation cancelled by user")
+        except EOFError:
+            raise PasswordPromptError("Interactive password prompt requires a TTY")
         except Exception as e:
             logging.error(
                 f"Unexpected error during password prompt: {e}", exc_info=True
@@ -204,6 +206,8 @@ def prompt_existing_password(
             print(colored("\nOperation cancelled by user.", "yellow"))
             logging.info("Existing password prompt interrupted by user.")
             raise PasswordPromptError("Operation cancelled by user")
+        except EOFError:
+            raise PasswordPromptError("Interactive password prompt requires a TTY")
         except Exception as e:
             logging.error(
                 f"Unexpected error during existing password prompt: {e}",

src/utils/seed_prompt.py

@@ -106,6 +106,8 @@ def _masked_input_posix(prompt: str) -> str:
 
 def masked_input(prompt: str) -> str:
     """Return input from the user while masking typed characters."""
+    if not sys.stdin.isatty():
+        raise EOFError("Interactive input requires a TTY")
     func = _masked_input_windows if sys.platform == "win32" else _masked_input_posix
     pause_console_logging()
     try: