feat(v2): T6 CollaborativePipeline 编排（快路径/协作循环/熔断/终审）

router_system/workspace.py

@@ -355,6 +355,18 @@ class Workspace:
         })
         self._commit(new)
 
+    def revise_plan(self, updates: Dict[str, str]) -> None:
+        """按 decision.patch_plan 修订既有 step 的 task（不改结构/顺序）。"""
+        if self._data.get("brief") is None:
+            raise ValueError("brief 尚未写入，无法修订 plan")
+        new = copy.deepcopy(self._data)
+        for pid, task in updates.items():
+            for p in new["brief"]["plan"]:
+                if p["id"] == pid:
+                    p["task"] = task
+                    break
+        self._commit(new)
+
     def mark_round(self) -> None:
         self._data["meta"]["round"] += 1