Fix signal script lint

Author: Pigbibi

scripts/post_shadow_signal_request.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import argparse
+from collections.abc import Mapping
 import datetime as dt
 import json
 import os

scripts/validate_latest_signal.py

@@ -9,7 +9,7 @@
 ROOT = Path(__file__).resolve().parents[1]
 sys.path.insert(0, str(ROOT / "src"))
 
-from ai_long_horizon_signal_pipelines import SignalValidationError, validate_signal
+from ai_long_horizon_signal_pipelines import SignalValidationError, validate_signal  # noqa: E402
 
 
 DEFAULT_SIGNAL_PATH = Path("data/output/latest_signal.json")