pub fn fetch_oxicode_home() -> Option<PathBuf>Expand description
Resolve the oxicode home directory through the unified Oxi home layout
($OXICODE_HOME, else <oxi_home>/oxicode, else ~/.oxi/oxicode).
The Foundation host is independent: OXICODE_HOME/OXI_HOME only
affect oxicode-local paths (legacy memory, migration checkpoints, etc.)
and do not change the Foundation root.