feat(qwen): add Qwen OAuth provider with portal request support

Based on #6079 by @tunamitom with critical fixes and comprehensive tests.

Changes from #6079:
- Fix: sanitization overwrite bug — Qwen message prep now runs AFTER codex
  field sanitization, not before (was silently discarding Qwen transforms)
- Fix: missing try/except AuthError in runtime_provider.py — stale Qwen
  credentials now fall through to next provider on auto-detect
- Fix: 'qwen' alias conflict — bare 'qwen' stays mapped to 'alibaba'
  (DashScope); use 'qwen-portal' or 'qwen-cli' for the OAuth provider
- Fix: hardcoded ['coder-model'] replaced with live API fetch + curated
  fallback list (qwen3-coder-plus, qwen3-coder)
- Fix: extract _is_qwen_portal() helper + _qwen_portal_headers() to replace
  5 inline 'portal.qwen.ai' string checks and share headers between init
  and credential swap
- Fix: add Qwen branch to _apply_client_headers_for_base_url for mid-session
  credential swaps
- Fix: remove suspicious TypeError catch blocks around _prompt_provider_choice
- Fix: handle bare string items in content lists (were silently dropped)
- Fix: remove redundant dict() copies after deepcopy in message prep
- Revert: unrelated ai-gateway test mock removal and model_switch.py comment deletion

New tests (30 test functions):
- _qwen_cli_auth_path, _read_qwen_cli_tokens (success + 3 error paths)
- _save_qwen_cli_tokens (roundtrip, parent creation, permissions)
- _qwen_access_token_is_expiring (5 edge cases: fresh, expired, within skew,
  None, non-numeric)
- _refresh_qwen_cli_tokens (success, preserve old refresh, 4 error paths,
  default expires_in, disk persistence)
- resolve_qwen_runtime_credentials (fresh, auto-refresh, force-refresh,
  missing token, env override)
- get_qwen_auth_status (logged in, not logged in)
- Runtime provider resolution (direct, pool entry, alias)
- _build_api_kwargs (metadata, vl_high_resolution_images, message formatting,
  max_tokens suppression)

hermes_cli/main.py

@@ -918,6 +918,7 @@ def select_provider_and_model(args=None):
         "openrouter": "OpenRouter",
         "nous": "Nous Portal",
         "openai-codex": "OpenAI Codex",
+        "qwen-oauth": "Qwen OAuth",
         "copilot-acp": "GitHub Copilot ACP",
         "copilot": "GitHub Copilot",
         "anthropic": "Anthropic",
@@ -947,6 +948,7 @@ def select_provider_and_model(args=None):
         ("openrouter", "OpenRouter (100+ models, pay-per-use)"),
         ("anthropic", "Anthropic (Claude models — API key or Claude Code)"),
         ("openai-codex", "OpenAI Codex"),
+        ("qwen-oauth", "Qwen OAuth (reuses local Qwen CLI login)"),
         ("copilot", "GitHub Copilot (uses GITHUB_TOKEN or gh auth token)"),
         ("huggingface", "Hugging Face Inference Providers (20+ open models)"),
     ]
@@ -1043,6 +1045,8 @@ def select_provider_and_model(args=None):
         _model_flow_nous(config, current_model, args=args)
     elif selected_provider == "openai-codex":
         _model_flow_openai_codex(config, current_model)
+    elif selected_provider == "qwen-oauth":
+        _model_flow_qwen_oauth(config, current_model)
     elif selected_provider == "copilot-acp":
         _model_flow_copilot_acp(config, current_model)
     elif selected_provider == "copilot":
@@ -1359,6 +1363,56 @@ def _model_flow_openai_codex(config, current_model=""):
 
 
 
+_DEFAULT_QWEN_PORTAL_MODELS = [
+    "qwen3-coder-plus",
+    "qwen3-coder",
+]
+
+
+def _model_flow_qwen_oauth(_config, current_model=""):
+    """Qwen OAuth provider: reuse local Qwen CLI login, then pick model."""
+    from hermes_cli.auth import (
+        get_qwen_auth_status,
+        resolve_qwen_runtime_credentials,
+        _prompt_model_selection,
+        _save_model_choice,
+        _update_config_for_provider,
+        DEFAULT_QWEN_BASE_URL,
+    )
+    from hermes_cli.models import fetch_api_models
+
+    status = get_qwen_auth_status()
+    if not status.get("logged_in"):
+        print("Not logged into Qwen CLI OAuth.")
+        print("Run: qwen auth qwen-oauth")
+        auth_file = status.get("auth_file")
+        if auth_file:
+            print(f"Expected credentials file: {auth_file}")
+        if status.get("error"):
+            print(f"Error: {status.get('error')}")
+        return
+
+    # Try live model discovery, fall back to curated list.
+    models = None
+    try:
+        creds = resolve_qwen_runtime_credentials(refresh_if_expiring=True)
+        models = fetch_api_models(creds["api_key"], creds["base_url"])
+    except Exception:
+        pass
+    if not models:
+        models = list(_DEFAULT_QWEN_PORTAL_MODELS)
+
+    default = current_model or (models[0] if models else "qwen3-coder-plus")
+    selected = _prompt_model_selection(models, current_model=default)
+    if selected:
+        _save_model_choice(selected)
+        _update_config_for_provider("qwen-oauth", DEFAULT_QWEN_BASE_URL)
+        print(f"Default model set to: {selected} (via Qwen OAuth)")
+    else:
+        print("No change.")
+
+
+
 def _model_flow_custom(config):
     """Custom endpoint: collect URL, API key, and model name.