fix(auth): set active_provider after hermes auth add qwen-oauth

hermes auth add qwen-oauth called pool.add_entry() but never wrote to
providers["qwen-oauth"] or set active_provider in auth.json.
_model_section_has_credentials() checks get_active_provider() first; with
active_provider unset and no api_key_env_vars configured for oauth_external
providers, the setup wizard reported "No inference provider configured" even
after a successful Qwen CLI OAuth login.

Add _mark_qwen_oauth_active() in auth.py: writes a minimal provider state
entry (base_url for display only) and calls _save_provider_state() to set
active_provider. The function deliberately does not copy the api_key — that
lives in the Qwen CLI credential file managed by _save_qwen_cli_tokens /
resolve_qwen_runtime_credentials and must not be duplicated in auth.json
where it would become stale.

pool.add_entry() is retained so "hermes auth list" continues to show the entry.
Runtime credential resolution continues to use resolve_qwen_runtime_credentials.

Mirrors the fix applied to openai-codex (#37517) and xai-oauth (#37576).

hermes_cli/auth_commands.py

@@ -367,6 +367,7 @@ def auth_add_command(args) -> None:
 
     if provider == "qwen-oauth":
         creds = auth_mod.resolve_qwen_runtime_credentials(refresh_if_expiring=False)
+        auth_mod._mark_qwen_oauth_active(creds)
         label = (getattr(args, "label", None) or "").strip() or label_from_token(
             creds["api_key"],
             _oauth_default_label(provider, len(pool.entries()) + 1),