Rename task update tool to patch_tasks

tests/state.test.ts

@@ -353,7 +353,7 @@ test("loads the latest valid mutation snapshot from a session branch", () => {
     type: "message",
     message: {
       role: "toolResult",
-      toolName: index === 0 ? "add_task" : "update_task",
+      toolName: index === 0 ? "add_task" : "patch_tasks",
       details: { action: "add", snapshot, affected: [] },
     },
   }));
@@ -362,6 +362,25 @@ test("loads the latest valid mutation snapshot from a session branch", () => {
   assert.deepEqual(state.list().map((task) => task.name), ["First", "Second"]);
 });
 
+test("loads legacy update_task mutation snapshots", () => {
+  const completed = new TaskState();
+  completed.add([{ name: "Legacy completed task", status: "done" }]);
+  const branch = [
+    {
+      type: "message",
+      message: {
+        role: "toolResult",
+        toolName: "update_task",
+        details: { action: "update", snapshot: completed.snapshot(), affected: [] },
+      },
+    },
+  ];
+
+  const state = new TaskState();
+  state.loadFromSession({ sessionManager: { getBranch: () => branch } } as never);
+  assert.deepEqual(state.list().map((task) => task.name), ["Legacy completed task"]);
+});
+
 test("loads a persisted automatic clear after task tool snapshots", () => {
   const completed = new TaskState();
   completed.add([{ name: "Completed", status: "done" }]);