News informational-only: gate sentiment bonus/penalty off by default

Add NewsConfig.sentiment_affects_signals (default False), gating the +5
aligned-sentiment confidence bonus and the 10-pt news_conflict penalty.
With event_risk_caps_signals already False, live decisions are now pure
technical, matching the backtester (use_news=False). Warnings and the
sentiment display are unchanged. Adds a gating regression test.

Claude-Session: https://claude.ai/code/session_01FMaaPdrrrQuh1VvGQH1icN

config.py

@@ -173,6 +173,11 @@ class NewsConfig:
     # entered near USD releases OUTPERFORM (+0.475R vs +0.256R avg).
     # Audit 2026-07-11 via backtest/research/calendar_store.
     event_risk_caps_signals: bool = False
+    # Whether headline sentiment moves the SIGNAL (aligned: +5 confidence;
+    # conflicting: 10-point penalty). Warnings are always emitted
+    # regardless. Default False = news is informational only; decisions
+    # are pure technical, matching the backtester (use_news=False).
+    sentiment_affects_signals: bool = False
     # Wider stay-out window after a high-impact release that surprised
     # vs forecast (inline releases use post_event_buffer_minutes).
     post_event_surprise_buffer_minutes: int = 45