feat: unify model listing logic into a single v1_models module

Consolidates LiteLLM and GitHub Copilot model fetching logic into a unified
module that supports standard /v1/models endpoints with automatic SSL
verification skipping for local/private IPs and Copilot token exchange.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: James Zhu

README.md

@@ -108,7 +108,7 @@ Create a `providers.json` file in `~/.config/code-assistant-manager/` or your pr
     "my-litellm": {
       "endpoint": "https://api.example.com:4142",
       "api_key_env": "API_KEY_LITELLM",
-      "list_models_cmd": "python -m code_assistant_manager.litellm_models",
+      "list_models_cmd": "python -m code_assistant_manager.v1_models",
       "supported_client": "claude,codex,qwen,copilot",
       "description": "My LiteLLM Proxy"
     }

README_zh.md

@@ -104,7 +104,7 @@ pip install -e ".[dev]"
     "my-litellm": {
       "endpoint": "https://api.example.com:4142",
       "api_key_env": "API_KEY_LITELLM",
-      "list_models_cmd": "python -m code_assistant_manager.litellm_models",
+      "list_models_cmd": "python -m code_assistant_manager.v1_models",
       "supported_client": "claude,codex,qwen,copilot",
       "description": "我的 LiteLLM 代理"
     }

code_assistant_manager/copilot_models.py

@@ -119,8 +119,7 @@ class EndpointManager:
 
     # Supported internal modules for model listing
     INTERNAL_MODEL_MODULES = (
-        "code_assistant_manager.litellm_models",
-        "code_assistant_manager.copilot_models",
+        "code_assistant_manager.v1_models",
     )
 
     # Proxy environment variables to manage