feat: add Alibaba Cloud provider and Anthropic base_url override (#1673)

Add Alibaba Cloud (DashScope) as a first-class inference provider
using the Anthropic-compatible endpoint. This gives access to Qwen
models (qwen3.5-plus, qwen3-max, qwen3-coder-plus, etc.) through
the same api_mode as native Anthropic.

Also add ANTHROPIC_BASE_URL env var support so users can point the
Anthropic provider at any compatible endpoint.

Changes:
- auth.py: Add alibaba ProviderConfig + ANTHROPIC_BASE_URL on anthropic
- models.py: Add alibaba to catalog, labels, aliases (dashscope/aliyun/qwen), provider order
- runtime_provider.py: Add alibaba resolution (anthropic_messages api_mode) + ANTHROPIC_BASE_URL
- model_metadata.py: Add Qwen model context lengths (128K)
- config.py: Add DASHSCOPE_API_KEY, DASHSCOPE_BASE_URL, ANTHROPIC_BASE_URL env vars

Usage:
  hermes --provider alibaba --model qwen3.5-plus
  # or via aliases:
  hermes --provider qwen --model qwen3-max

hermes_cli/runtime_provider.py

@@ -276,15 +276,30 @@ def resolve_runtime_provider(
                 "No Anthropic credentials found. Set ANTHROPIC_TOKEN or ANTHROPIC_API_KEY, "
                 "run 'claude setup-token', or authenticate with 'claude /login'."
             )
+        # Support custom Anthropic-compatible endpoints via ANTHROPIC_BASE_URL
+        base_url = os.getenv("ANTHROPIC_BASE_URL", "").strip() or "https://api.anthropic.com"
         return {
             "provider": "anthropic",
             "api_mode": "anthropic_messages",
-            "base_url": "https://api.anthropic.com",
+            "base_url": base_url,
             "api_key": token,
             "source": "env",
             "requested_provider": requested_provider,
         }
 
+    # Alibaba Cloud / DashScope (Anthropic-compatible endpoint)
+    if provider == "alibaba":
+        creds = resolve_api_key_provider_credentials(provider)
+        base_url = creds.get("base_url", "").rstrip("/") or "https://dashscope-intl.aliyuncs.com/apps/anthropic"
+        return {
+            "provider": "alibaba",
+            "api_mode": "anthropic_messages",
+            "base_url": base_url,
+            "api_key": creds.get("api_key", ""),
+            "source": creds.get("source", "env"),
+            "requested_provider": requested_provider,
+        }
+
     # API-key providers (z.ai/GLM, Kimi, MiniMax, MiniMax-CN)
     pconfig = PROVIDER_REGISTRY.get(provider)
     if pconfig and pconfig.auth_type == "api_key":