fix: ensure researcher agent uses web search tool instead of generating URLs (#702) (#704)

* fix: ensure researcher agent uses web search tool instead of generating URLs (#702)

- Add enforce_researcher_search configuration option (default: True) to control web search requirement
- Strengthen researcher prompts in both English and Chinese with explicit instructions to use web_search tool
- Implement validate_web_search_usage function to detect if web search tool was used during research
- Add validation logic that warns when researcher doesn't use web search tool
- Enhance logging for web search tools with special markers for easy tracking
- Skip validation during unit tests to avoid test failures
- Update _execute_agent_step to accept config parameter for proper configuration access

This addresses issue #702 where the researcher agent was generating URLs on its own instead of using the web search tool.

* fix: addressed the code review comment

* fix the unit test error and update the code

src/prompts/researcher.md

@@ -37,7 +37,8 @@ You have access to two types of tools:
 3. **Plan the Solution**: Determine the best approach to solve the problem using the available tools.
 4. **Execute the Solution**:
    - Forget your previous knowledge, so you **should leverage the tools** to retrieve the information.
-   - Use the {% if resources %}**local_search_tool** or{% endif %}**web_search** or other suitable search tool to perform a search with the provided keywords.
+   - **CRITICAL**: You MUST use the {% if resources %}**local_search_tool** or{% endif %}**web_search** tool to search for information. NEVER generate URLs on your own. All URLs must come from tool results.
+   - **MANDATORY**: Always perform at least one web search using the **web_search** tool at the beginning of your research. This is not optional.
    - When the task includes time range requirements:
      - Incorporate appropriate time-based search parameters in your queries (e.g., "after:2020", "before:2023", or specific date ranges)
      - Ensure search results respect the specified time constraints.
@@ -71,6 +72,8 @@ You have access to two types of tools:
 
 # Notes
 
+- **CRITICAL**: NEVER generate URLs on your own. All URLs must come from search tool results. This is a mandatory requirement.
+- **MANDATORY**: Always start with a web search. Do not rely on your internal knowledge.
 - Always verify the relevance and credibility of the information gathered.
 - If no URL is provided, focus solely on the search results.
 - Never do any math or any file operations.

src/prompts/researcher.zh_CN.md

@@ -37,7 +37,8 @@ CURRENT_TIME: {{ CURRENT_TIME }}
 3. **规划解决方案**：确定使用可用工具解决问题的最佳方法。
 4. **执行解决方案**：
    - 忘记你之前的知识，所以你**应该利用工具**来检索信息。
-   - 使用{% if resources %}**local_search_tool**或{% endif %}**web_search**或其他合适的搜索工具以提供的关键词执行搜索。
+   - **关键要求**：你必须使用{% if resources %}**local_search_tool**或{% endif %}**web_search**工具搜索信息。绝对不能自己生成URL。所有URL必须来自工具结果。
+   - **强制要求**：在研究开始时必须使用**web_search**工具至少执行一次网络搜索。这不是可选项。
    - 当任务包括时间范围要求时：
      - 在查询中纳入适当的基于时间的搜索参数（如"after:2020"、"before:2023"或特定日期范围）
      - 确保搜索结果尊重指定的时间约束。
@@ -66,6 +67,8 @@ CURRENT_TIME: {{ CURRENT_TIME }}
 
 # 注意
 
+- **关键要求**：绝对不能自己生成URL。所有URL必须来自搜索工具结果。这是强制要求。
+- **强制要求**：始终从网络搜索开始。不要依赖你的内部知识。
 - 始终验证收集的信息的相关性和可信度。
 - 如果未提供URL，仅关注搜索结果。
 - 不要进行任何数学运算或文件操作。