fix(providers): remove Qwen provider support

Qwen OAuth flow (portal.qwen.ai) stopped working reliably; drop the
executor, registry entry, OAuth provider/service, token refresh
profile, usage handler, and related test coverage and baselines.

open-sse/providers/registry/index.js

@@ -75,7 +75,6 @@ import p72 from "./perplexity.js";
 import p73 from "./perplexity-agent.js";
 import p74 from "./playht.js";
 import p75 from "./qoder.js";
-import p76 from "./qwen.js";
 import p77 from "./recraft.js";
 import p78 from "./runwayml.js";
 import p79 from "./sdwebui.js";
@@ -198,7 +197,6 @@ export default [
   p73,
   p74,
   p75,
-  p76,
   p77,
   p78,
   p79,