feat(provider): add CodeBuddy CN provider (copilot.tencent.com)

Add Tencent CodeBuddy CN (codebuddy-cn) OAuth provider with full support:
OAuth login (GET poll with state query param), token refresh, 15-model
catalog, /v2 inference endpoint, forced streaming, OpenAI-style reasoning,
and per-model capabilities. Renamed from codebuddy to codebuddy-cn to allow
a future codebuddy-ai variant.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/shared/components/OAuthModal.js

@@ -157,7 +157,7 @@ export default function OAuthModal({ isOpen, provider, providerInfo, onSuccess,
       setError(null);
 
       // Device code flow providers
-      const deviceCodeProviders = ["github", "qwen", "kiro", "kimi-coding", "kilocode", "codebuddy", "qoder"];
+      const deviceCodeProviders = ["github", "qwen", "kiro", "kimi-coding", "kilocode", "codebuddy-cn", "qoder"];
       if (deviceCodeProviders.includes(provider)) {
         setIsDeviceCode(true);
         setStep("waiting");