[BUG] VS Code extension: renaming a session tab reverts to old name on Enter

### Preflight Checklist

- [x] I have searched existing issues and this hasn't been reported yet
- [x] This is a single bug report
- [x] I am using the latest version of Claude Code

### What's Wrong?

Renaming a session tab in the Claude Code VS Code extension's sidebar does not work. After typing a new name into the rename field and pressing Enter, the field resets back to the old name instead of committing the new one.

### What Should Happen?

Pressing Enter after typing a new session name should commit the rename and show the new name in the sidebar.

### Steps to Reproduce

1. Open the Claude Code sidebar in VS Code with at least one active session.
2. Click the rename (pencil) icon on a session tab.
3. Type a new name into the field.
4. Press Enter.
5. Observe: the field reverts to the original name instead of keeping the new one.

### Claude Model

Not sure / Multiple models

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

Unknown

### Claude Code Version

2.1.268 (Claude Code)

### Platform

Anthropic API

### Operating System

macOS

### Terminal/Shell

VS Code integrated terminal

### Additional Information

- VS Code version: 1.131.0
- Claude Code VS Code extension version: anthropic.claude-code 2.1.270
- OS: macOS 15.7.3 (Build 24G419)

Reproduce the rename flow in the Claude Code VS Code extension's sidebar using the listed steps, then trace the session-tab rename handling for the Enter key. Confirm that the new name is retained and shown after submission, including for the reported macOS and extension versions.

索引モデルが issue の本文から書いたものです。