fix(roundtable): 会商 Step2/Step3 沙箱产物按对话创建者解析，修复历史/跨用户查看不了

圆桌会商系统线程(metadata.thread_type==roundtable)的 Step2 席位/总控 +
Step3 报告/总结/大屏/结构化 沙箱产物(md/流程图/报告)落在创建者目录下，
之前按当前登录解析路径 + owner_check 校验 → 历史草稿重开或 taskId 会商被
其他账号打开时 403/404 查看不了。沿用任务深链对话方案(23e6685)扩展到圆桌：

- thread_paths._is_creator_shared_thread：taskId 或 thread_type==roundtable
  都解析到对话创建者(threads_meta.user_id)，覆盖所有线程路径关口
- ThreadMetaRepository.check_access：圆桌系统线程同样跳过 owner 过滤
  (artifacts 路由 owner_check 据此放行其他账号/历史查看)

线程 id 仅存在于草稿中，无关账号无法发现，与 taskId 共享模型一致。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

offline-backend-20260512/backend/CLAUDE.md

@@ -459,7 +459,7 @@ Operators upgrading an existing DB run the whole file (`USE <db>;` then execute)
 - Physical: `backend/.deer-flow/users/{user_id}/threads/{thread_id}/user-data/...`, `deer-flow/skills/`
 - Translation: `replace_virtual_path()` / `replace_virtual_paths_in_command()`
 - Detection: `is_local_sandbox()` checks `sandbox_id == "local"`
-- **`{user_id}` for path resolution = `resolve_path_user_id(thread_id)`, NOT the current login.** Task-deeplink conversations (rwfx/3qfx/xdfx, `threads_meta.metadata.taskId`) are shared across all users (see the `taskId` escape branches in `thread_meta/sql.py`), but generated files/uploads live under a *per-user* dir. Resolving by current login meant account B opening a shared task conversation 404'd on the md/artifacts account A generated ("切换账号后生成的文件找不到"). `deerflow/runtime/thread_paths.py` (`resolve_path_user_id` sync / `aresolve_path_user_id` async) resolves a task-shared thread to its **creator** (`threads_meta.user_id`), so every account reads/writes the same physical directory; personal threads resolve to the current login unchanged (no behavior change). Wired at every thread-path seam: write source `ThreadDataMiddleware.before_agent` (drives all sandbox writes via `thread_data` paths), `present_file_tool`, `uploads/manager.get_uploads_dir` + `uploads_middleware` + uploads router, artifact serving (`path_utils.{a,}resolve_thread_virtual_path` → artifacts/skills routers), embedded `client.get_artifact`. Positive (taskId→creator) results are cached process-wide (immutable mapping); any failure / memory-mode store / missing row falls back to the current login. **Caveat**: files a *non-creator* wrote into a shared thread before this fix stay orphaned under that writer's dir (no data loss); all new writes consolidate under the creator. Tests: `tests/test_thread_paths_owner.py`.
+- **`{user_id}` for path resolution = `resolve_path_user_id(thread_id)`, NOT the current login.** Task-deeplink conversations (rwfx/3qfx/xdfx, `threads_meta.metadata.taskId`) are shared across all users (see the `taskId` escape branches in `thread_meta/sql.py`), but generated files/uploads live under a *per-user* dir. Resolving by current login meant account B opening a shared task conversation 404'd on the md/artifacts account A generated ("切换账号后生成的文件找不到"). `deerflow/runtime/thread_paths.py` (`resolve_path_user_id` sync / `aresolve_path_user_id` async) resolves a task-shared thread to its **creator** (`threads_meta.user_id`), so every account reads/writes the same physical directory; personal threads resolve to the current login unchanged (no behavior change). Wired at every thread-path seam: write source `ThreadDataMiddleware.before_agent` (drives all sandbox writes via `thread_data` paths), `present_file_tool`, `uploads/manager.get_uploads_dir` + `uploads_middleware` + uploads router, artifact serving (`path_utils.{a,}resolve_thread_virtual_path` → artifacts/skills routers), embedded `client.get_artifact`. Positive (taskId→creator) results are cached process-wide (immutable mapping); any failure / memory-mode store / missing row falls back to the current login. **Caveat**: files a *non-creator* wrote into a shared thread before this fix stay orphaned under that writer's dir (no data loss); all new writes consolidate under the creator. **Extended to 圆桌会商 system threads** (`metadata.thread_type == "roundtable"` — Step 2 seats/coordinator + Step 3 report/summary/dashboard/structure, created by `multi_agent.py` with `_ROUNDTABLE_THREAD_METADATA`): their Step2/Step3 sandbox artifacts (md/流程图/报告) must stay viewable when a历史草稿 is reopened or a taskId会商 draft is opened by another account, so `thread_paths._is_creator_shared_thread(metadata)` treats both `taskId` **and** `thread_type=="roundtable"` as creator-shared, and `ThreadMetaRepository.check_access` (the artifacts router's `owner_check`) bypasses the owner filter for both — roundtable thread ids are only surfaced inside the owner's draft, so this does not let unrelated accounts *discover* others' 会商 files. Tests: `tests/test_thread_paths_owner.py`, `tests/test_thread_paths_roundtable.py`.
 
 **Sandbox Tools** (in `packages/harness/deerflow/sandbox/tools.py`):
 - `bash` - Execute commands with path translation and error handling