refactor: align display label and docs with sentiment_analyst rename

The agent ingests news, StockTwits, and Reddit, but CLI labels, the
README description, and the legacy shim docstring still framed it as
social-media-only. Updates all user-visible surfaces so the name and
the implementation match.

tradingagents/agents/utils/agent_states.py

@@ -51,7 +51,7 @@ class AgentState(MessagesState):
 
     # research step
     market_report: Annotated[str, "Report from the Market Analyst"]
-    sentiment_report: Annotated[str, "Report from the Social Media Analyst"]
+    sentiment_report: Annotated[str, "Report from the Sentiment Analyst"]
     news_report: Annotated[
         str, "Report from the News Researcher of current world affairs"
     ]