Models: add Qwen Portal OAuth support

src/agents/model-auth.ts

@@ -147,6 +147,10 @@ export function resolveEnvApiKey(provider: string): EnvApiKeyResult | null {
     return pick("OPENCODE_API_KEY") ?? pick("OPENCODE_ZEN_API_KEY");
   }
 
+  if (normalized === "qwen-portal") {
+    return pick("QWEN_OAUTH_TOKEN") ?? pick("QWEN_PORTAL_API_KEY");
+  }
+
   const envMap: Record<string, string> = {
     openai: "OPENAI_API_KEY",
     google: "GEMINI_API_KEY",