Function xdg_cache_home 

pub fn xdg_cache_home() -> PathBuf

Get XDG cache home directory.

Returns $XDG_CACHE_HOME or falls back to ~/.cache.

Embedders use this to compose their own cache paths:

use kaish_kernel::paths::xdg_cache_home;

let myapp_cache = xdg_cache_home().join("myapp");