Load a single MCP config file, returning None on any error.
Disabled servers are removed before per-server validation, so explicitly
denied entries can neither block loading nor surface to a caller inspecting
the config. The single-file counterpart to load_merged_mcp_configs_lenient
(which the trust prompt uses); this one has no production caller today and is
retained as the standalone lenient loader.
Config path to load.
Server names to remove before validation.
