fix: add thinking diagnostic log + skip retry for code-only chunks

Two changes to finish off the slow-translation issue:

1. agent.py: log the resolved thinking config at Agent init. Lets
   operators confirm from task logs that the thinking-disable fix is
   actually running (e.g. 'field=extra_body, applied_value={enable_thinking: False}')
   — critical for distinguishing 'fix not deployed' from 'fix not enough'.

2. segments_agent.py: when the whole chunk returns identical to source,
   skip the retry if the source has fewer than two 4+ letter English
   words. Technical docs (this client's WI/PRD docs) have many chunks
   that are pure codes/numbers/abbreviations (FRM-QAD-SQM-018, HNB-020,
   V1.0) — LLM correctly returns them unchanged, but the old code
   retried 3x. 4-letter threshold avoids matching 3-letter abbrevs
   like FRM/QAD/HNB.

docutranslate/agents/agent.py

@@ -540,6 +540,16 @@ class Agent:
         self.mt_domains = getattr(config, "custom_prompt", None)
         self.mt_glossary_dict = getattr(config, "glossary_dict", None)
 
+        # 诊断日志：确认 thinking 配置实际生效（用于排查 qwen3 推理模式未关闭的问题）
+        tm = get_thinking_mode(self.provider, self.model_id)
+        if tm is not None:
+            field, val_en, val_dis = tm
+            target_val = val_en if self.thinking == "enable" else val_dis
+            self.logger.info(
+                f"Agent thinking config: provider={self.provider}, model={self.model_id}, "
+                f"mode={self.thinking}, field={field}, applied_value={target_val}"
+            )
+
     def _estimate_tokens(self, text: str) -> int:
         """
         改进的纯 Python 估算，适配更多语言。

docutranslate/agents/segments_agent.py

@@ -137,6 +137,18 @@ class SegmentsTranslateAgent(Agent):
                 raise AgentResultError(f"Agent返回结果不是dict的json形式, result: {result}")
 
             if repaired_result == original_chunk:
+                # 启发式：如果原文几乎全是代码/数字/编号（真正的英文单词很少），
+                # LLM 原样返回是合理的，不应触发重试。技术文档常有这种 chunk。
+                # 用 4+ 字母的英文词作判据，排除 FRM/QAD/HNB 这类 3 字母缩写。
+                original_text = "".join(str(v) for v in original_chunk.values())
+                translatable_words = re.findall(r"\b[A-Za-z]{4,}\b", original_text)
+                if len(translatable_words) < 2:
+                    logger.info(
+                        f"翻译结果与原文相同，但原文几乎全是代码/数字/缩写（4字母以上词 {len(translatable_words)} 个），跳过重试。"
+                    )
+                    for key, value in repaired_result.items():
+                        repaired_result[key] = str(value)
+                    return repaired_result
                 raise AgentResultError("翻译结果与原文完全相同，疑似翻译失败，将进行重试。")
 
             original_keys = set(original_chunk.keys())