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/config.py

@@ -492,6 +492,29 @@ OPTIONAL_ENV_VARS = {
         "password": False,
         "category": "provider",
     },
+    "ANTHROPIC_BASE_URL": {
+        "description": "Custom Anthropic-compatible API base URL (e.g. Alibaba Cloud DashScope)",
+        "prompt": "Anthropic Base URL",
+        "url": "",
+        "password": False,
+        "category": "provider",
+        "advanced": True,
+    },
+    "DASHSCOPE_API_KEY": {
+        "description": "Alibaba Cloud DashScope API key for Qwen models",
+        "prompt": "DashScope API Key",
+        "url": "https://modelstudio.console.alibabacloud.com/",
+        "password": True,
+        "category": "provider",
+    },
+    "DASHSCOPE_BASE_URL": {
+        "description": "Custom DashScope base URL (default: international endpoint)",
+        "prompt": "DashScope Base URL",
+        "url": "",
+        "password": False,
+        "category": "provider",
+        "advanced": True,
+    },
     "OPENCODE_ZEN_API_KEY": {
         "description": "OpenCode Zen API key (pay-as-you-go access to curated models)",
         "prompt": "OpenCode Zen API key",