Function set_config_dir_override 

pub fn set_config_dir_override(path: Option<PathBuf>)

What: Set or clear the process-wide configuration directory override.

Inputs:

• path: Some(dir) to use dir as the config root; None to restore default resolution.

Output:

• None (side effect: subsequent path helpers resolve under the override).

Details:

• Called once at startup when --config-dir is passed, before logging initializes.
• Also used by tests to isolate path resolution; ignores a poisoned lock by recovering it.