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/executors/codebuddy-cn.js

@@ -0,0 +1,36 @@
+import { DefaultExecutor } from "./default.js";
+
+/**
+ * CodeBuddyExecutor — talks to https://copilot.tencent.com/v2/chat/completions
+ *
+ * CodeBuddy is OpenAI-compatible but rejects non-stream chat requests
+ * (HTTP 400, code 11101 "Non-stream chat request is currently not supported").
+ * The same-format (openai→openai) translator path leaves body.stream as the
+ * client sent it, so we force it true here — 9router still re-aggregates the
+ * SSE into a JSON response for non-streaming clients.
+ */
+export class CodeBuddyExecutor extends DefaultExecutor {
+  constructor() {
+    super("codebuddy-cn");
+  }
+
+  transformRequest(model, body, stream, credentials) {
+    const transformed = super.transformRequest(model, body, stream, credentials);
+    transformed.stream = true;
+
+    // CodeBuddy only surfaces model reasoning when the request carries the CLI's
+    // OpenAI-style params: reasoning_effort + reasoning_summary:"auto". 9router's
+    // thinking pipeline sets reasoning_effort only when the client asks, and never
+    // sets reasoning_summary — so reasoning never shows. Mirror the CLI here.
+    const eff = transformed.reasoning_effort;
+    if (eff === "none" || eff === "off") {
+      delete transformed.reasoning_effort; // gateway has no "none" — just omit
+    } else {
+      if (!eff) transformed.reasoning_effort = "medium";
+      transformed.reasoning_summary = "auto";
+    }
+    return transformed;
+  }
+}
+
+export default CodeBuddyExecutor;