refactor(vscode-ide-companion): simplify ACP connection and cleanup configurations

- Remove .claude from .gitignore
- Update CSS file path in eslint config
- Simplify VS Code extension title
- Remove unused keybinding for openChat command
- Delete unused auth constants file
- Simplify ACP connection by removing backend parameter
- Move authMethod to acpTypes
- Restrict ACP backend to Qwen only
- Remove backend property from connection state
- Minor formatting update in webview index.tsx

packages/vscode-ide-companion/src/constants/auth.ts

@@ -1,7 +0,0 @@
-/**
- * @license
- * Copyright 2025 Qwen Team
- * SPDX-License-Identifier: Apache-2.0
- */
-
-export const authMethod = 'qwen-oauth';