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>

open-sse/services/tokenRefresh/providers.js

@@ -524,3 +524,57 @@ export async function refreshCopilotToken(githubAccessToken, log) {
   }
   }, log);
 }
+
+// CodeBuddy (Tencent) refresh — POST /v2/plugin/auth/token/refresh with the
+// refresh token carried in the X-Refresh-Token header (not a form body),
+// matching the official CodeBuddy CLI. Response: { code: 0, data: <token> }.
+export async function refreshCodebuddyToken(refreshToken, log) {
+  if (!refreshToken) return null;
+  return dedupRefresh("codebuddy-cn", refreshToken, async () => {
+    const oauth = PROVIDER_OAUTH["codebuddy-cn"] || {};
+    const response = await fetch(oauth.refreshUrl, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+        Accept: "application/json",
+        "User-Agent": oauth.userAgent,
+        "X-Requested-With": "XMLHttpRequest",
+        "X-Domain": "copilot.tencent.com",
+        "X-Refresh-Token": refreshToken,
+        "X-Auth-Refresh-Source": "plugin",
+        "X-Product": "SaaS",
+      },
+      body: "{}",
+    });
+
+    if (!response.ok) {
+      const errorText = await response.text();
+      log?.error?.("TOKEN_REFRESH", "Failed to refresh CodeBuddy token", {
+        status: response.status,
+        error: errorText,
+      });
+      return null;
+    }
+
+    const data = await response.json();
+    if (data.code !== 0 || !data.data?.accessToken) {
+      log?.error?.("TOKEN_REFRESH", "CodeBuddy token refresh returned no token", {
+        code: data.code,
+        msg: data.msg,
+      });
+      return null;
+    }
+
+    log?.info?.("TOKEN_REFRESH", "Successfully refreshed CodeBuddy token", {
+      hasNewAccessToken: !!data.data.accessToken,
+      hasNewRefreshToken: !!data.data.refreshToken,
+      expiresIn: data.data.expiresIn,
+    });
+
+    return {
+      accessToken: data.data.accessToken,
+      refreshToken: data.data.refreshToken || refreshToken,
+      expiresIn: data.data.expiresIn,
+    };
+  }, log);
+}