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/app/api/oauth/[provider]/[action]/route.js

@@ -151,7 +151,7 @@ export async function GET(request, { params }) {
         : undefined;
       
       // Providers that don't use PKCE for device code
-      const noPkceDeviceProviders = ["github", "kiro", "kimi-coding", "kilocode", "codebuddy", "qoder"];
+      const noPkceDeviceProviders = ["github", "kiro", "kimi-coding", "kilocode", "codebuddy-cn", "qoder"];
       let deviceData;
       if (noPkceDeviceProviders.includes(provider)) {
         deviceData = await requestDeviceCode(provider, undefined, deviceOptions);
@@ -271,7 +271,7 @@ export async function POST(request, { params }) {
       }
 
       // Providers that don't use PKCE for device code
-      const noPkceProviders = ["github", "kimi-coding", "kilocode", "codebuddy"];
+      const noPkceProviders = ["github", "kimi-coding", "kilocode", "codebuddy-cn"];
       let result;
       if (noPkceProviders.includes(provider)) {
         result = await pollForToken(provider, deviceCode);

src/app/api/providers/[id]/test/testUtils.js

@@ -90,7 +90,7 @@ const OAUTH_TEST_CONFIG = {
     authHeader: "Authorization",
     authPrefix: "Bearer ",
   },
-  codebuddy: { tokenExists: true },
+  "codebuddy-cn": { tokenExists: true },
 };
 
 async function probeClineAccessToken(accessToken) {