feat: add SkillRegistry for agent integration

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/agents/skill_registry.py

@@ -0,0 +1,46 @@
+"""
+Skill Registry - Agent 运行时加载 Skills
+"""
+from typing import Optional
+from app.database import async_session
+from app.services.skill_service import SkillService
+
+# 缓存：agent_type -> list[Skill]
+_skill_cache: dict[str, list] = {}
+
+async def load_skills_for_agent(agent_type: str, force_reload: bool = False) -> list:
+    """加载指定 Agent 类型的可用 Skills"""
+    if not force_reload and agent_type in _skill_cache:
+        return _skill_cache[agent_type]
+    async with async_session() as db:
+        svc = SkillService(db)
+        skills = await svc.get_by_agent_type(agent_type)
+        _skill_cache[agent_type] = skills
+        return skills
+
+def get_skills_for_agent(agent_type: str) -> list:
+    """同步接口：返回缓存的 Skills（供 Agent 节点调用）"""
+    return _skill_cache.get(agent_type, [])
+
+def build_skill_context(agent_type: str) -> str:
+    """
+    构建 Skill 上下文，供注入到 Agent 系统提示
+    格式：Skill 名称 + 描述 + 工具列表
+    """
+    skills = get_skills_for_agent(agent_type)
+    if not skills:
+        return ""
+    lines = ["\n\n【可用的 Skills】"]
+    for s in skills:
+        tools_str = ", ".join(s.tools) if s.tools else "无"
+        lines.append(f"""
+## {s.name}
+- 描述: {s.description or '无'}
+- 工具: {tools_str}
+- 指令: {s.instructions[:200]}...""" if len(s.instructions) > 200 else f"- 指令: {s.instructions}")
+    return "\n".join(lines)
+
+def clear_cache():
+    """清除缓存（配置变更时调用）"""
+    global _skill_cache
+    _skill_cache = {}