Auto-clear completed todo trees

tests/state.test.ts

@@ -1,6 +1,6 @@
 import assert from "node:assert/strict";
 import test from "node:test";
-import { TaskState } from "../src/state.ts";
+import { TASK_STATE_ENTRY_TYPE, TaskState } from "../src/state.ts";
 import { TaskValidationError } from "../src/types.ts";
 
 function names(state: TaskState): string[] {
@@ -362,6 +362,30 @@ test("loads the latest valid mutation snapshot from a session branch", () => {
   assert.deepEqual(state.list().map((task) => task.name), ["First", "Second"]);
 });
 
+test("loads a persisted automatic clear after task tool snapshots", () => {
+  const completed = new TaskState();
+  completed.add([{ name: "Completed", status: "done" }]);
+  const branch = [
+    {
+      type: "message",
+      message: {
+        role: "toolResult",
+        toolName: "update_task",
+        details: { action: "update", snapshot: completed.snapshot(), affected: [] },
+      },
+    },
+    {
+      type: "custom",
+      customType: TASK_STATE_ENTRY_TYPE,
+      data: { tasks: [], nextId: 1 },
+    },
+  ];
+
+  const state = new TaskState();
+  state.loadFromSession({ sessionManager: { getBranch: () => branch } } as never);
+  assert.deepEqual(state.snapshot(), { tasks: [], nextId: 1 });
+});
+
 test("rejects terminal controls and bidirectional overrides without changing state", () => {
   const state = new TaskState();
   state.add([{ name: "Safe", description: "Line one\nLine two" }]);