feat(skill): add clarify-user-intent atom

paperforge/skills/paperforge/atoms/clarify-user-intent.md

@@ -1,3 +1,41 @@
 # clarify-user-intent
 
-Clarify the user's intent before dispatching to a skill workflow.
+Clarifies ambiguous user intent when SKILL.md cannot confidently route.
+
+## Trigger conditions
+
+- Input is too short or vague
+- Input matches multiple top-level intents
+- Required object (paper key/DOI/title) is missing
+- User says "这篇" but no unique paper is locked in context
+
+## Interaction rules
+
+1. Explain briefly what PaperForge can do
+2. Present options matching the 5 research intents + mechanical commands
+3. Let user choose or provide more details
+4. Maximum 2 rounds of clarification; after that, report inability to route
+
+Two-round limit: 最多两轮。两轮后仍无法确定，告知用户无法路由。
+
+## Fixed question pattern (Chinese)
+
+```
+我可以帮你做这几类事：
+
+1. 找某篇文章
+2. 找一批相关论文
+3. 找支持某个观点/参数/术语的证据
+4. 精读一篇文章
+5. 记录到项目阅读笔记 / 保存
+
+你现在更想做哪一种？如果你已经有 paper key / DOI / 标题，也可以直接发给我。
+```
+
+## Output
+
+Returns one: `clarified_intent` matched to the compound's top-level intents.
+
+## Two-round limit rule
+
+最多两轮。两轮后仍无法确定，告知用户无法路由。