Function socket_path 

pub fn socket_path(root: &Path) -> PathBuf

Resolves the socket path for a given watched root directory.

Tries in order:

1. $XDG_RUNTIME_DIR/ixd/{hash}.sock
2. $HOME/.local/run/ixd/{hash}.sock
3. /tmp/ixd-{uid}-{hash}.sock

Where hash is the first 16 hex characters of XXH64(canonical_root, 0).