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/roots.py

@@ -0,0 +1,95 @@
+"""Workspace roots — the directories a session is allowed to touch.
+
+A Cowork session is "orphan": it owns a per-conversation **scratch** dir (the primary root,
+writable, the default save location) and may gain access to additional folders, each chosen
+read-only or read-write. The same `list[RootDir]` object is shared by reference across the
+PermissionEngine (scoping), the file toolkit (resolution), and the context injector (so the
+agent is told which dirs it has), so Slice C can mutate it in place at runtime and all three
+see the change. Index 0 is always the primary.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Any, Iterable
+
+
+@dataclass
+class RootDir:
+    path: Path
+    writable: bool = False
+    label: str = ""  # display name; defaults to the dir's basename
+
+    def __post_init__(self) -> None:
+        self.path = Path(self.path).expanduser().resolve()
+        if not self.label:
+            self.label = self.path.name or str(self.path)
+
+    def to_dict(self) -> dict[str, Any]:
+        return {"path": str(self.path), "writable": self.writable, "label": self.label}
+
+
+def normalize_roots(roots: Iterable[Any] | None) -> list[RootDir]:
+    """Coerce a mixed list (RootDir | dict{path,writable,label} | str/Path) into RootDirs.
+    Bare str/Path entries are treated as read-only; pass dicts/RootDirs to grant write.
+    """
+    out: list[RootDir] = []
+    for r in roots or []:
+        if isinstance(r, RootDir):
+            out.append(r)
+        elif isinstance(r, dict):
+            out.append(
+                RootDir(
+                    path=r["path"],
+                    writable=bool(r.get("writable", False)),
+                    label=r.get("label", ""),
+                )
+            )
+        elif isinstance(r, (str, Path)):
+            out.append(RootDir(path=r, writable=False))
+        else:  # duck-typed object with .path/.writable
+            out.append(
+                RootDir(
+                    path=getattr(r, "path"),
+                    writable=bool(getattr(r, "writable", False)),
+                )
+            )
+    return out
+
+
+def render_context(roots: list[RootDir]) -> str:
+    """The `<system-context>` body listing the dirs available this turn. Empty when no roots."""
+    if not roots:
+        return ""
+    lines = ["Available directories (you may use file/shell tools within these):"]
+    has_side_scratch = any(i > 0 and r.label == "scratch" for i, r in enumerate(roots))
+    for i, r in enumerate(roots):
+        access = "read-write" if r.writable else "read-only"
+        if i == 0 and r.label == "scratch":
+            tag = " — primary scratch, the default place to save files"
+        elif i == 0:
+            tag = " — the session's workspace (relative paths resolve here)"
+        elif r.label == "scratch":
+            tag = (
+                " — your scratch directory: temporary files, and artifacts you don't "
+                "want to leave inside the workspace"
+            )
+        else:
+            tag = ""
+        lines.append(f"- {r.path} [{access}]{tag}")
+    if has_side_scratch:
+        lines.append(
+            "Relative paths resolve against the workspace; pass an absolute path to use "
+            "another directory. Writes are only allowed in read-write directories. Put "
+            "reports, analyses, and other non-repo deliverables in the scratch directory "
+            "(they appear in the user's Artifacts panel) — write into the workspace only "
+            "for changes that belong in it."
+        )
+    else:
+        lines.append(
+            "Relative paths resolve against the primary directory; pass an absolute path to use "
+            "another directory. Writes are only allowed in read-write directories. If the user "
+            "cares where a deliverable lands, ask; otherwise save it in the primary scratch."
+        )
+    return "\n".join(lines)