[Bug] Agent does not mark the final todo item as complete after multi-step tasks

[yc-eagle]

Description

When the agent executes a multi-step task, it generates a todo list in the UI. After all steps have been successfully completed, the final todo item remains in a "loading/spinning" state indefinitely, giving the user the false impression that the task is still ongoing.

Steps to Reproduce

1. Start a new session with the agent in Web mode.
2. Issue a multi-step command. Example: "帮我安装 DSH-Web 这个插件"
3. Wait for the agent to complete all steps.
4. Observe the agent's todo list in the UI.

Testing & Observations

Test 1: Install DSH-Web (multi-step)

• The plugin was successfully installed.
• The todo list showed 4 items, with the 4th ("Report activation step to user") stuck spinning indefinitely.
• The stuck state persisted after restarting the DSH web service.
• The agent was able to close it only when I explicitly told it to: "请把刚才那个任务标记为完成".

Test 2: Install AnySearch (single-step)

• The plugin was successfully installed.
• No todo list was generated, so there was no item to get stuck.
• This confirms the issue is specific to multi-step task planning.

Test 3: Create a test.txt file (single-step)

• The file was created successfully.
• No todo list was generated.

Expected Behavior

All todo items should be marked as "completed" after the final step is done. The agent should automatically close the task lifecycle.

Actual Behavior

The final todo item remains in a loading/spinning state indefinitely. The agent only closes it when explicitly told to do so.

Additional Context

• OS: Windows 11
• DSH Version: 0.1.2-alpha.5
• This appears to be a systemic issue with the agent's task lifecycle management (todo.update not being called after task completion), not specific to any plugin or action.

Proposed Fix Suggestion

The agent should call todo.update to mark the final item as "completed" after all steps are done and the final user notification is delivered.

Related Discussions

This is different from #2027 (which is about /goal in minimal mode missing update_goal tool). My issue is in the default Web mode and specifically about the todo list UI state not being finalized.