/news: normalize rounded-zero score so "-0.00" renders as "+0.00"

A balanced feed (XAU and USD means nearly cancelling) yields a tiny
negative net that "+.2f" rendered as "-0.00" — seen live 2026-08-03.
Regression test uses that day's actual per-currency means (300 tests).

Claude-Session: https://claude.ai/code/session_017975c1TufZ3xRYAq8iWTCS

telegram_bot.py

@@ -1036,6 +1036,8 @@ async def cmd_status(update: Update, context: ContextTypes.DEFAULT_TYPE) -> None
 
 def _news_text(context: FundamentalContext, engine: NewsEngine) -> str:
     net, desc = engine.get_pair_sentiment(XAUUSD, context)
+    if round(net, 2) == 0:
+        net = 0.0  # a tiny negative mean would render as "-0.00"
     lines = [
         "📰 *XAU/USD News Score*\n",
         f"*Net score:* `{net:+.2f}` — {desc}",