translate every llm-facing string-literal in
backend/app/services/report_agent.py — the four tool-description
constants, the plan/section/chat system+user prompts, the react loop
templates, the inline messages re-injected during the section and chat
loops, the _execute_tool error returns, and the plan_outline default and
fallback outline content. preserve every {interpolation} token, the
literal final answer: trigger and <tool_call> xml tag, the four primary
tool names, and all three get_language_instruction() postfix call sites.
also switch the unused-tools join separator from "、" to ", " so it
renders naturally inside the now-english react templates.
removes the chinese language bias that the english postfix alone could
not overcome — under accept-language: en the report agent now produces
english-flavoured analytical reports and chat replies; under
accept-language: zh the postfix continues to steer the model into
chinese with no semantic delta. logger calls (#6) and docstrings or
comments (#7) are deliberately untouched.
Closes#5
22a3ca7af5