A tracker a template’s checkpoint deposits into. Created through the same
CLI path as newgit tracker create, so trackers stay CLI-managed and
templates never hand-write tracker TOML.
Starter resource templates. companions are additional resource
definitions the template depends on, and companion_trackers are lanes
it deposits into; both are created alongside it when absent (e.g. the
user-owned pnpm-store that deps depends on, or the db-snapshots
lane a Postgres dump lands in).