feat: implement provider deactivation and enhance configuration updates

- Added a new function to deactivate the active provider without deleting credentials, facilitating smoother transitions between different provider types.
- Updated the model flow logic to ensure the active provider is correctly set in the configuration, including handling custom endpoints and OAuth providers.
- Improved error handling in the CLI to consistently format authentication error messages.
- Enhanced the model selection process to reflect the effective provider based on configuration and environment variables.

cli.py

@@ -782,8 +782,7 @@ class HermesCLI:
                 timeout_seconds=float(os.getenv("HERMES_NOUS_TIMEOUT_SECONDS", "15")),
             )
         except Exception as exc:
-            from hermes_cli.auth import AuthError
-            message = format_auth_error(exc) if isinstance(exc, AuthError) else str(exc)
+            message = format_auth_error(exc)
             self.console.print(f"[bold red]{message}[/]")
             return False