Display active model + reasoning effort in VS Code extension UI

Problem

The VS Code extension has no persistent indicator of the active model or reasoning effort level. The statusLine setting is terminal/CLI-only and doesn't render in the extension panel, and SessionStart hook stdout is injected into the model's context rather than shown to the user. The only way to check the current model in the extension is to manually run /status or /model each session — easy to forget, especially when switching models mid-session or across worktrees.

Request

Show the active model and effort level somewhere persistent in the extension UI — e.g. a small label in the chat panel header, or a VS Code status bar item. Ideally it updates live when the model/effort changes via /model.

Why it matters

• Model and effort materially affect output quality, speed, and cost; users need to know what's active without an extra command.
• Users running multiple sessions/worktrees can lose track of which model each is on.
• Parity with the terminal, where statusLine already covers this.

Possible approaches

1. Let the existing statusLine config render in the extension too.
2. A dedicated VS Code status bar item (claudeCode.* setting to toggle).
3. A persistent label in the chat panel header.