fix(cli): read root-level provider and base_url from config.yaml into model config (#3112)

When users write root-level provider and base_url in config.yaml
(instead of nesting under model:), these keys were never merged into
defaults['model']. The CLI reads them from CLI_CONFIG['model']['provider']
so root-level keys were silently ignored, causing fallback to OpenRouter.

Merge root-level provider and base_url into defaults['model'] after
handling the model key, so custom/local provider configs work regardless
of nesting.

Cherry-picked from PR #2283 by ygd58. Fixes #2281.

cli.py

@@ -261,6 +261,18 @@ def load_cli_config() -> Dict[str, Any]:
                 elif isinstance(file_config["model"], dict):
                     # Old format: model is a dict with default/base_url
                     defaults["model"].update(file_config["model"])
+
+            # Root-level provider and base_url override model config.
+            # Users may write:
+            #   model: kimi-k2.5:cloud
+            #   provider: custom
+            #   base_url: http://localhost:11434/v1
+            # These root-level keys must be merged into defaults["model"] so
+            # they are picked up by CLI provider resolution.
+            if "provider" in file_config and file_config["provider"]:
+                defaults["model"]["provider"] = file_config["provider"]
+            if "base_url" in file_config and file_config["base_url"]:
+                defaults["model"]["base_url"] = file_config["base_url"]
             
             # Deep merge file_config into defaults.
             # First: merge keys that exist in both (deep-merge dicts, overwrite scalars)