/clear doesn't update session title — stale title and context usage persist after clearing

Description

After running /clear in a chat session, a new session is started internally, but the tab/session title is not updated. It continues to display the title from the previous conversation, along with stale context usage stats.

Steps to Reproduce

1. Start a Claude Code session and have a conversation long enough that it gets a meaningful title.
2. Run /clear to start a new session.
3. Observe the session tab title — it still shows the old conversation's title.
4. Observe the context usage indicator — it still shows the previous session's usage rather than the fresh session's usage.

Expected Behavior

After /clear, the session title should reset (e.g., to "New Session" or be cleared), and the context usage should reset to reflect the new, empty session.

Actual Behavior

The session tab title remains set to the old conversation's title. The context usage indicator continues to display the stale value from the previous session.

Impact

Users see misleading information: the tab title implies they are continuing an old conversation, and the context usage meter shows incorrect (inflated) usage for what is actually a fresh session.