feat(tasks): 完整结果另存 result_text_full，详情不再只剩 2000 字

旧链路三层截断：sandbox stdout 截 2000 字、worker 写回截
4000 字，长答案尾部在详情里永远查不到（只把上限调大是
把截断点后移，不是修掉）。修法：截断版保持不变（列表/
摘要用），完整版另存：
- sandbox _result_from_runner/_parse_host_result（local 与
  docker dispatch 路）回包新增 stdout_full（上限 200000 字，
  只防无界增长）；goal 路结论在尾部、tail 已保结论，不动。
- worker _write_execution_result 新增 result_text_full 列
  （_ensure_result_columns + server migrate_tasks_table 幂等
  补列），终局与取消分支均透传 stdout_full。
- server：任务 dict 加 result_full_available（不直接塞全文
  进列表负载），新增 GET /tasks/{id}/result-full（read 权限
  同款校验，无完整版时 404，不回摘要冒充完整）。
单测：test_queue_sandbox 45 项（含新增 stdout_full 1 项）、
test_marker_tools 30 项。

cloud/worker.py

@@ -1345,7 +1345,8 @@ class Worker:
         except Exception:
             return
         for name, coltype in {
-                "result_text": "TEXT", "error_text": "TEXT",
+                "result_text": "TEXT", "result_text_full": "TEXT",
+                "error_text": "TEXT",
                 "actual_model": "TEXT", "started_at": "REAL",
                 "finished_at": "REAL", "child_pid": "INTEGER",
                 "executor": "TEXT", "pr_url": "TEXT",
@@ -1439,7 +1440,11 @@ class Worker:
                                 error_text=None, actual_model=None,
                                 started_at=None, finished_at=None,
                                 child_pid=None, turn_id=None,
-                                root_turn_id=None, only_if_status=None):
+                                root_turn_id=None, only_if_status=None,
+                                result_full=None):
+        # result_full：完整 stdout（dispatch/docker 路由 sandbox
+        # 的 stdout_full）；截断版 result_text 保持 4000 不变作
+        # 摘要，完整版另存 result_text_full 供详情/端点取。
         """把执行结果写进 tasks 新列；老库缺列时先迁移再写。
 
         turn_id/root_turn_id 只在新值非空时覆盖：某轮没产出
@@ -1461,14 +1466,17 @@ class Worker:
             if only_if_status is not None:
                 status_clause = " AND status = ?"
                 extra = (only_if_status,)
+            full = (result_full[:200000] if result_full else None)
             if child_pid is None:
                 cur = conn.execute(
-                    "UPDATE tasks SET result_text = ?, error_text = ?,"
+                    "UPDATE tasks SET result_text = ?,"
+                    " result_text_full = ?, error_text = ?,"
                     " actual_model = ?, started_at = ?, finished_at = ?,"
                     " turn_id = COALESCE(?, turn_id),"
                     " root_turn_id = COALESCE(?, root_turn_id),"
                     " updated_at = ? WHERE id = ?" + status_clause,
                     ((result_text or "")[:21000] if result_text else None,
+                     full,
                      (error_text or "")[:4000] if error_text else None,
                      actual_model, started_at, finished_at,
                      turn_id, root_turn_id,
@@ -1476,13 +1484,15 @@ class Worker:
                 )
             else:
                 cur = conn.execute(
-                    "UPDATE tasks SET result_text = ?, error_text = ?,"
+                    "UPDATE tasks SET result_text = ?,"
+                    " result_text_full = ?, error_text = ?,"
                     " actual_model = ?, started_at = ?, finished_at = ?,"
                     " child_pid = ?,"
                     " turn_id = COALESCE(?, turn_id),"
                     " root_turn_id = COALESCE(?, root_turn_id),"
                     " updated_at = ? WHERE id = ?" + status_clause,
                     ((result_text or "")[:21000] if result_text else None,
+                     full,
                      (error_text or "")[:4000] if error_text else None,
                      actual_model, started_at, finished_at, child_pid,
                      turn_id, root_turn_id,
@@ -5072,7 +5082,8 @@ class Worker:
                 started_at=started_at, finished_at=time.time(),
                 turn_id=(result or {}).get("turn_id"),
                 root_turn_id=(result or {}).get("root_turn_id"),
-                only_if_status="interrupted")
+                only_if_status="interrupted",
+                result_full=(result or {}).get("stdout_full"))
             # P1：取消分支先记一条成本再返回（与配额中断收尾
             # 同款记账点）。旧版这里直接返回 cost_record_id=None，
             # 被取消前已花的模型费用就从账上丢了；取消不等于没
@@ -5160,7 +5171,8 @@ class Worker:
                 finished_at=finished_at,
                 turn_id=(result or {}).get("turn_id"),
                 root_turn_id=(result or {}).get("root_turn_id"),
-                only_if_status=final)
+                only_if_status=final,
+                result_full=(result or {}).get("stdout_full"))
         # 附件暂存清理：任务终局后删 bundle 目录（重试走已存在
         # 续跑，文件已在 worktree 里，不再需要暂存）。
         self._cleanup_task_seed(task)