feat: v0.2.0 - add system tray, clean up unused role field

- Replace text '+' icon with centered SVG plus icon for the add-provider button
- Add system tray: minimize-to-tray and quit-from-tray menu (minimize hides window, close exits app)
- Remove unused model role field (no functional effect, only stored/displayed)
- Fix multiple providers showing as active in Kimi Code mode: only the default_model's provider is marked active
- Copy /reload to clipboard after provider switch as a convenience hint
- Bump version to 0.2.0

src/types/index.ts

@@ -34,8 +34,6 @@ export interface Model {
   model: string;
   max_context_size: number;
   display_name: string | null;
-  /** Optional model role, e.g. Sonnet/Opus/Fable/Haiku for Claude-style mapping. */
-  role?: string | null;
   /** Whether the model declares extended context / thinking support. */
   supports_1m?: boolean;
   /** Agent-specific capability flags (e.g. Kimi Code `capabilities`). */