[Bug] UI clicks ignored on first attempt — requires clicking, pausing, then clicking again (macOS)

### Short summary

Many UI buttons and session items require clicking, pausing briefly, then clicking again before the action takes effect (macOS).

### Affected version or release

1.0.22

### Installation context

_No response_

### What happened?

Many UI interactions in the GitHub Copilot app don't respond to a single click. Instead, I have to click once, pause briefly, and then click again for the action to register. The first click appears to be swallowed or ignored — only after a short pause does the second click take effect.

This affects various buttons and session items throughout the app.

Environment:
- **OS:** macOS 15.5 (24G517)

### Steps to reproduce

1. Open the GitHub Copilot app.
2. Click on a button or a session item (e.g., switching sessions, action buttons).
3. Observe that the first click does not register — there is no visible response.
4. Pause briefly, then click the same target again — the action now takes effect.

### Expected behavior

A single click should trigger the intended action immediately.

### Additional context

- This is reproducible consistently across different buttons and session interactions.
- It is **not** a rapid double-click — the issue is that the first click is ignored and a second click after a brief pause is needed.
- Debug logs:

まず、macOS 15.5 上の GitHub Copilot app 1.0.22 で最初のクリックが無視される挙動を再現し、セッション項目とアクションボタンの両方を確認します。これらの操作で使われている共通のクリック処理経路を追跡します。影響を受ける UI 全体で、1 回のクリックによって意図した表示上のアクションが直ちに実行されれば完了です。

索引モデルが issue の本文から書いたものです。