fix(oauth): repair qwen + codebuddy-cn device-code endpoints (#7517)

Both device-code providers failed at the upstream request (surfacing in the
companion extension as 'ошибка сервера OmniRoute'). Diagnosed by calling the
upstream endpoints directly:

- qwen: QWEN_CONFIG used the bare host qwen.ai, whose /api/v1/oauth2/device/code
  and /token paths return 404 Not Found. The working qwen-code device flow lives
  at chat.qwen.ai (verified: 200 + a valid device_code/user_code). Point both
  URLs at chat.qwen.ai.
- codebuddy-cn: the Tencent state endpoint reads 'platform' from the QUERY
  string, not the JSON body. Sending it only in the body returned
  400 {"code":10001,"msg":"platform is empty"}. Passing ?platform=CLI
  returned 200 with {code:0, data:{state, authUrl}}. Build the stateUrl with the
  platform query param (body kept as-is).

Validation: live upstream calls returned 200 for both corrected requests (device
flow can't be hit from CI). Regression guard: tests/unit/oauth-device-code-endpoints.test.ts.

src/lib/oauth/constants/oauth.ts

@@ -74,8 +74,10 @@ export const CODEX_CONFIG = {
 // Qwen OAuth Configuration (Device Code Flow with PKCE)
 export const QWEN_CONFIG = {
   clientId: resolvePublicCred("qwen_id", "QWEN_OAUTH_CLIENT_ID"),
-  deviceCodeUrl: "https://qwen.ai/api/v1/oauth2/device/code",
-  tokenUrl: "https://qwen.ai/api/v1/oauth2/token",
+  // Host is chat.qwen.ai — the bare qwen.ai host 404s on these paths (verified: the qwen-code
+  // device flow lives at chat.qwen.ai, returning a valid device_code; qwen.ai returns Not Found).
+  deviceCodeUrl: "https://chat.qwen.ai/api/v1/oauth2/device/code",
+  tokenUrl: "https://chat.qwen.ai/api/v1/oauth2/token",
   scope: "openid profile email model.completion",
   codeChallengeMethod: "S256",
 };

src/lib/oauth/providers/codebuddy-cn.ts

@@ -38,7 +38,10 @@ export const codebuddyCn = {
   flowType: "device_code" as const,
 
   requestDeviceCode: async (config: CodeBuddyConfig): Promise<CodeBuddyDeviceCodeResponse> => {
-    const response = await fetch(config.stateUrl, {
+    // CodeBuddy reads `platform` from the QUERY string, not the JSON body — sending it only in the
+    // body returns 400 "platform is empty" (verified). Pass it as a query param; body kept as-is.
+    const stateUrl = `${config.stateUrl}?platform=${encodeURIComponent(config.platform)}`;
+    const response = await fetch(stateUrl, {
       method: "POST",
       headers: {
         "Content-Type": "application/json",

tests/unit/oauth-device-code-endpoints.test.ts

@@ -0,0 +1,32 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { dirname, resolve } from "node:path";
+
+// Regression guards for the two device-code providers that returned "ошибка сервера OmniRoute":
+//
+//   qwen        — QWEN_CONFIG pointed at the bare host qwen.ai, whose device/token paths 404.
+//                 The working qwen-code device flow lives at chat.qwen.ai (verified live: 200 +
+//                 a valid device_code). Guard: the config uses chat.qwen.ai, never bare qwen.ai.
+//   codebuddy-cn— the Tencent state endpoint reads `platform` from the QUERY string, not the JSON
+//                 body; body-only returned 400 "platform is empty" (verified live). The fix passes
+//                 it as a query param. Guard: requestDeviceCode builds the URL with ?platform=.
+//
+// Source-level: the real validation is the live upstream 200 (can't be hit from CI); these pin
+// the exact change so a revert to the broken host / body-only platform fails here.
+const here = dirname(fileURLToPath(import.meta.url));
+const read = (p: string) => readFileSync(resolve(here, "../..", p), "utf8");
+
+test("qwen device-code config uses chat.qwen.ai (not the 404ing bare qwen.ai)", () => {
+  const oauth = read("src/lib/oauth/constants/oauth.ts");
+  const qwenBlock = oauth.slice(oauth.indexOf("QWEN_CONFIG"), oauth.indexOf("QWEN_CONFIG") + 700);
+  assert.match(qwenBlock, /chat\.qwen\.ai\/api\/v1\/oauth2\/device\/code/, "deviceCodeUrl host");
+  assert.match(qwenBlock, /chat\.qwen\.ai\/api\/v1\/oauth2\/token/, "tokenUrl host");
+  assert.doesNotMatch(qwenBlock, /"https:\/\/qwen\.ai\//, "must not use the bare qwen.ai host");
+});
+
+test("codebuddy-cn device-code sends platform as a query param (not body-only)", () => {
+  const cb = read("src/lib/oauth/providers/codebuddy-cn.ts");
+  assert.match(cb, /\?platform=\$\{encodeURIComponent\(config\.platform\)\}/, "platform query param");
+});