Validate a shapes `.rds` file in isolation
validate_read_shp.RdReads the `.rds` at `shp_path` and checks two invariants: (1) the object is a non-empty named list, and (2) every `admin<N>Pcod` column referenced inside any layer has a corresponding top-level `admin<N>_*` element. Emits one cli alert per check; returns the structured `list(status, summary, issues)` result invisibly.
Value
Invisibly, a list with components `status` (`"pass"`, `"warn"`, or `"fail"`), `summary` (one-line string), and `issues` (list of issue records).