Agent chat title is automatically replaced by a temporary subtask

## Description

An agent chat with an existing, representative title can be automatically renamed when the user asks for a narrower follow-up task. The resulting title describes the latest action rather than the overall session.

For example, I started a session to diagnose VS Code webview service-worker failures. The chat was initially titled:

> Debug webview service worker

Later, after the investigation was complete, I asked the agent to draft a GitHub issue comment containing the findings. The agent automatically renamed the chat to:

> Draft webview bug report

Drafting the report was only a follow-up step. The overall subject of the session was still the webview investigation, so the new title made the session less recognizable.

## Expected behavior

Once a chat has a meaningful title, a narrower follow-up task should not automatically replace it.

An automatic rename should happen only when:

- the current title is still a placeholder, or
- the overall subject of the conversation has materially changed.

Explicit user-requested renames should continue to replace the current title.

## Actual behavior

The agent invoked the rename operation again and supplied a title based on the latest subtask. The rename operation applied that title even though the chat already had a descriptive title and the overall subject had not changed.

Neither the rename operation nor a skill generated the title independently. The problem was that the agent decided to rename and over-weighted the latest user request.

## Suggested improvement

Automatic title handling could prevent this in one or both of the following ways:

1. Do not automatically rename a chat that already has a non-placeholder title unless the conversation's overall subject clearly changed.
2. Before applying an automatic rename, compare the proposed title with the existing title and the conversation-wide topic. Reject or discourage titles that describe only a temporary workflow step such as "draft report", "run tests", or "create PR".

After noticing the problem, the title was manually corrected to:

> Diagnosing VS Code webview failures

This title covers both the investigation and its reporting follow-up.