Config source precedence

When configuration is moved/renamed or when settings are derived from environment variables, ensure (1) the dotenv loader points to the correct file path/name and (2) there is an explicit precedence order for derived settings (env-provided values override generated/default values).

Apply this as two concrete checks:

• Config file correctness: If you migrate .env (or stop using default.env), update the code that resolves the env file path (e.g., avoid loaders that still call something like get_abs_path('.env') when the new location is usr/.env or similar). Also remove references to env filenames you don’t actually use.
• Precedence for derived settings: For settings like tokens/keys, implement a deterministic rule: read the override from dotenv/env first; if missing/empty, fall back to create_* or other defaults.

Example pattern:

import dotenv

def apply_settings(copy: dict) -> None:
    # precedence: env override > generated default
    external_key = dotenv.get_dotenv_value("A0_EXTERNAL_API_KEY")
    if external_key:
        copy["mcp_server_token"] = external_key
    else:
        copy["mcp_server_token"] = create_auth_token()