feat: OpenMesh 基础平台与 MD/PDF 转换技能

- 后端: coworker 智能体框架, WS API, 文件上传, 附件处理
- 前端: Open WebUI, 文件全量走 upload API (含 MD/TXT/JSON 等文本类)
- 技能: md-to-office (pandoc + wkhtmltopdf)
- 修复: 上传文件路径丢失, Agent 搜索浪费, 输出文件跑到 uploads/
- 打包: PyInstaller one-dir, 预打包 pandoc/wkhtmltopdf/chromium

coworker/skills/__init__.py

@@ -0,0 +1,20 @@
+from .base import Skill, SkillLoader, skill_catalog_text, skill_tools
+from .store import (
+    SessionSkillStore,
+    SkillStore,
+    effective_skills,
+    save_skill_tool,
+    validate_name,
+)
+
+__all__ = [
+    "Skill",
+    "SkillLoader",
+    "skill_catalog_text",
+    "skill_tools",
+    "SkillStore",
+    "SessionSkillStore",
+    "effective_skills",
+    "save_skill_tool",
+    "validate_name",
+]