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/agents/registry.py

@@ -0,0 +1,28 @@
+"""Agent registry — resolves a persona id to its runtime Agent.
+
+Delegates to the persona registry (``coworker.personas``) so built-in surfaces and
+markdown/third-party personas resolve through one path. MyHelper is a legacy personal-helper
+persona resolved directly (kept for sessions that still reference it).
+Imports of the persona registry are lazy to avoid an import cycle (personas → agents builders).
+"""
+
+from __future__ import annotations
+
+from .base import Agent
+from .myhelper import myhelper_agent
+
+
+def get_agent(name: str) -> Agent:
+    name = name or "code"
+    if name == "myhelper":
+        return myhelper_agent()
+    from ..personas.registry import get_registry
+
+    return get_registry().agent(name)
+
+
+def list_agents() -> list[dict]:
+    # Session surfaces shown in the new-session picker (enabled + surfaced personas).
+    from ..personas.registry import get_registry
+
+    return get_registry().sidebar()