fix: 添加 Explore agent 系统提示词模板并优化日志级别

- 添加 exploreAgentSystemPrompt 模板用于匹配 Claude Code Explore 子代理
- 将详细的 prompt 内容从 error 日志移至 warn 级别，减少日志噪音

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/validators/clients/claudeCodeValidator.js

@@ -64,9 +64,8 @@ class ClaudeCodeValidator {
       const rawText = typeof entry?.text === 'string' ? entry.text : ''
       const { bestScore } = bestSimilarityByTemplates(rawText)
       if (bestScore < threshold) {
-        logger.error(
-          `Claude system prompt similarity below threshold: score=${bestScore.toFixed(4)}, threshold=${threshold}, prompt=${rawText}`
-        )
+        logger.error(`Claude system prompt similarity below threshold: score=${bestScore.toFixed(4)}, threshold=${threshold}`)
+        logger.warn(`Claude system prompt detail: ${rawText}`)
         return false
       }
     }