Add configuration for Kettle (/buddy) bubble persistence

Request

Add configuration settings to control the buddy (/buddy) speech bubble persistence, including:

• Configurable timeout duration (how long bubbles stay visible before auto-dismissing)
• Option to disable auto-dismiss entirely (permanently persistent bubbles)

Current behavior

Kettle's suggestions disappear automatically after a short, fixed duration. This makes it difficult to read the suggestion before it vanishes.

Desired behavior

Users should be able to configure:

1. The bubble dismiss timeout (in seconds/milliseconds)
2. An option to keep bubbles persistent until manually dismissed

This could be added to settings.json similar to other UI customization options like spinnerTipsEnabled.