Function registry_dir 

pub fn registry_dir(homes: &HarnessHomes) -> PathBuf

Directory holding the live-session registry for the configured Claude home.

HarnessHomes::claude_code points at <claude home>/projects, so the registry is that directory’s sibling. Deriving it keeps one configuration knob (CLAUDE_CONFIG_DIR, through HarnessHomes) rather than adding a second that could disagree with it.