Allow customizing companion name

Feature Request

The companion dragon (currently hardcoded as "Waffle") should have a configurable name.

Use Case

Users who want to personalize their Claude Code experience should be able to rename the companion to something meaningful to them (e.g., "Guigui").

Proposed Solution

Add a companionName key to settings.json (or a dedicated companion config section) that allows users to set a custom name:

{
  "companion": {
    "name": "Guigui"
  }
}

The system prompt and UI should then reference the configured name instead of the hardcoded default.

Alternatives Considered

• Addressing the companion by a different name in conversation works conversationally, but the UI and system prompt still reference "Waffle," creating a mismatch.