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/tools/plan.py

@@ -0,0 +1,43 @@
+"""The `propose_plan` tool — the agent presents its plan and asks to start executing.
+
+Registered only when the session starts in plan mode. Like `request_directory`, it is
+intercepted by the TurnEngine: it emits a PLAN_PROPOSED event and waits for the user's
+out-of-band decision. Approval flips the live PermissionEngine out of plan mode (same
+session, full exploration context kept); rejection returns the user's feedback so the
+agent can revise the plan. The callable here is only a schema carrier + a safe fallback
+for surfaces without an approver.
+"""
+
+from __future__ import annotations
+
+from aisuite.agents import ToolMetadata, tool
+
+
+def propose_plan_tool() -> object:
+    def propose_plan(plan: str) -> dict:
+        """Present your implementation plan to the user for approval. Use this once you
+        have explored enough to commit to an approach: summarize what you'll change, in
+        which files, and how you'll verify it. If approved, the session switches out of
+        read-only plan mode and you implement the plan; if rejected, revise it using the
+        feedback in the result. Don't start describing implementation steps as if you
+        were doing them — propose first.
+        """
+        # Real handling lives in the engine (it needs the out-of-band approval round-trip).
+        # This body only runs if no approver is wired (e.g. a headless surface).
+        return {
+            "approved": False,
+            "error": "plan approval isn't available in this surface",
+        }
+
+    return tool(
+        propose_plan,
+        metadata=ToolMetadata(
+            category="planning",
+            risk_level="low",
+            capabilities=["plan"],
+            description=(
+                "Present the implementation plan for user approval; approval exits "
+                "read-only plan mode and starts execution."
+            ),
+        ),
+    )