feat(i18n): localize researchers, risk debators, research mgr, trader

output_language config now propagates to every user-facing agent.
Previously only the four analysts and portfolio manager respected
the setting, producing partial-localization reports with English
debate text interleaved with non-English analyst sections. Verified
live: 7 agents produce Chinese output when config is set to Chinese.

#575

tradingagents/agents/utils/agent_utils.py

@@ -24,8 +24,10 @@ def get_language_instruction() -> str:
     """Return a prompt instruction for the configured output language.
 
     Returns empty string when English (default), so no extra tokens are used.
-    Only applied to user-facing agents (analysts, portfolio manager).
-    Internal debate agents stay in English for reasoning quality.
+    Applied to every agent whose output reaches the saved report —
+    analysts, researchers, debaters, research manager, trader, and
+    portfolio manager — so a non-English run produces a fully localized
+    report rather than a mix of languages.
     """
     from tradingagents.dataflows.config import get_config
     lang = get_config().get("output_language", "English")