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/auth.py

@@ -138,6 +138,15 @@ PROVIDER_REGISTRY: Dict[str, ProviderConfig] = {
         auth_type="api_key",
         inference_base_url="https://api.anthropic.com",
         api_key_env_vars=("ANTHROPIC_API_KEY", "ANTHROPIC_TOKEN", "CLAUDE_CODE_OAUTH_TOKEN"),
+        base_url_env_var="ANTHROPIC_BASE_URL",
+    ),
+    "alibaba": ProviderConfig(
+        id="alibaba",
+        name="Alibaba Cloud (DashScope)",
+        auth_type="api_key",
+        inference_base_url="https://dashscope-intl.aliyuncs.com/apps/anthropic",
+        api_key_env_vars=("DASHSCOPE_API_KEY",),
+        base_url_env_var="DASHSCOPE_BASE_URL",
     ),
     "minimax-cn": ProviderConfig(
         id="minimax-cn",