feat: Add Azure Foundry provider with OpenAI/Anthropic API mode selection

Add support for Azure Foundry as a new inference provider. Azure Foundry
endpoints can use either OpenAI-style (/v1/chat/completions) or
Anthropic-style (/v1/messages) API formats.

Changes:
- Add azure-foundry to PROVIDER_REGISTRY (auth.py)
- Add azure-foundry overlay in HERMES_OVERLAYS (providers.py)
- Add empty model list for azure-foundry (models.py)
- Add _model_flow_azure_foundry() interactive setup (main.py)
- Add azure-foundry runtime resolution with api_mode support (runtime_provider.py)
- Add AZURE_FOUNDRY_API_KEY and AZURE_FOUNDRY_BASE_URL env vars (config.py)

Usage:
  hermes model -> More providers -> Azure Foundry

The setup wizard prompts for:
- Endpoint URL
- API format (OpenAI or Anthropic-style)
- API key
- Model name

Configuration is saved to config.yaml (model.provider, model.base_url,
model.api_mode, model.default) and ~/.hermes/.env (AZURE_FOUNDRY_API_KEY).

hermes_cli/auth.py

@@ -356,6 +356,14 @@ PROVIDER_REGISTRY: Dict[str, ProviderConfig] = {
         api_key_env_vars=(),
         base_url_env_var="BEDROCK_BASE_URL",
     ),
+    "azure-foundry": ProviderConfig(
+        id="azure-foundry",
+        name="Azure Foundry",
+        auth_type="api_key",
+        inference_base_url="",  # User-provided endpoint
+        api_key_env_vars=("AZURE_FOUNDRY_API_KEY",),
+        base_url_env_var="AZURE_FOUNDRY_BASE_URL",
+    ),
 }