Inf-3: `list_country_shapes()` — return tibble of available countries and admin levels from bundled registry

[EBukin]

What to build

A new exported function list_country_shapes() that reads inst/wb_shapes_registry.yaml (Inf-2) and returns a tibble of available countries and admin levels. Parallel in design to the existing list_hex_vars().

Offline-capable — no network call. The deployer calls this at the start of 01-shapes.qmd to discover what ISO-3 codes and admin levels are queryable via get_country_shapes().

Signature and return value

list_country_shapes()

Returns a tibble with one row per (country × admin level):

Column	Type	Notes
iso3	character	ISO-3 country code
country_name	character	English country name
admin_level	integer	0, 1, or 2
level_name	character	Human-readable label, e.g. "Province", "District"
available	logical	TRUE if present in parquet
last_updated	Date	Date of last ETL run for this country

Usage in template

# Browse all available countries
list_country_shapes()

# Filter to a specific country
list_country_shapes() |>
  dplyr::filter(iso3 == "RWA")

# Find all countries with admin2 coverage
list_country_shapes() |>
  dplyr::filter(admin_level == 2, available)

Implementation notes

• Reads bundled YAML via internal read_shapes_registry()
• No network dependency
• @family data-input (same family group as list_hex_vars())
• Roxygen examples must pass devtools::check() without network access

Acceptance criteria

• list_country_shapes() is exported and documented
• Returns one row per (iso3 × admin_level)
• Works offline (no HTTP calls)
• devtools::check() examples pass headlessly
• Unit test: returns a tibble with correct columns; Rwanda rows present; result is filterable

Blocked by

#146 (Inf-2) — requires the registry YAML to be present.