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.

tests/translator/golden-url-header.test.js

@@ -18,7 +18,7 @@ const SPECIAL_CRED = {
 // Chúng được lock riêng ở 11-provider edge tests / unit test chuyên biệt.
 const SPECIALIZED = new Set([
   "antigravity", "azure", "gemini-cli", "github", "iflow", "qoder", "kiro",
-  "codex", "cursor", "vertex", "vertex-partner", "qwen", "opencode",
+  "codex", "cursor", "vertex", "vertex-partner", "opencode",
   "opencode-go", "grok-web", "perplexity-web", "ollama-local", "commandcode",
   "xiaomi-tokenplan", "mimo-free",
 ]);