Function parse_workspace_package_names 

pub fn parse_workspace_package_names(metadata_json: &str) -> Vec<String>

Parse cargo metadata --no-deps’s JSON for the names of packages defined in the workspace itself — never a dependency, which is exactly the distinction that keeps a freshness fix from also discarding a downloaded crate’s compiled artifacts on every worktree switch. Pure, so the parse is tested against fixture text without a cargo on the test machine.