Reduce LLM rewrite calls and add report intro conclusion

ai_daily_report/assemble.py

@@ -35,13 +35,28 @@ def _source_link(item: NewsItem) -> str:
     return source
 
 
+def _fallback_intro(items: list[NewsItem]) -> str:
+    count = len(items)
+    return f"今天共聚合 {count} 条 AI 动态，覆盖模型能力、产品应用、基础设施、资本与治理等方向。"
+
+
+def _fallback_conclusion(items: list[NewsItem]) -> str:
+    sections = [section for section in SECTION_ORDER if any(item.section == section for item in items)]
+    if sections:
+        return "总体看，今日 AI 动态主要集中在" + "、".join(sections[:4]) + "等方向，后续仍需持续观察落地进展。"
+    return "总体看，今日 AI 动态仍在持续演进，后续需要关注产品落地和生态变化。"
+
+
 def assemble_markdown(items: list[NewsItem], guide: dict[str, Any] | None = None) -> tuple[str, dict[str, Any]]:
-    guide = guide or {"theme": "", "threads": []}
+    guide = guide or {"intro": "", "theme": "", "threads": [], "conclusion": ""}
     lines: list[str] = []
 
+    intro = _ensure_sentence(str(guide.get("intro") or "")) or _fallback_intro(items)
+    lines.extend(["## 引言", "", f"> {intro}", ""])
+
     theme = _clean_text(str(guide.get("theme") or ""))
     if theme:
-        lines.extend(["## 导览", "", f"> {theme}", ""])
+        lines.extend(["## 导览", "", f"> {_ensure_sentence(theme)}", ""])
 
     item_number = 1
     for section in SECTION_ORDER:
@@ -72,6 +87,9 @@ def assemble_markdown(items: list[NewsItem], guide: dict[str, Any] | None = None
                 continue
             lines.extend([f"- **{title}**", f"  {text}", ""])
 
+    conclusion = _ensure_sentence(str(guide.get("conclusion") or "")) or _fallback_conclusion(items)
+    lines.extend(["## 总结", "", f"> {conclusion}", ""])
+
     markdown = "\n".join(lines).strip()
     report = validate_markdown(markdown, items)
     return markdown, report