Feature() crashes on countries that declare a table but ship no microdata (e.g. Nepal)

[ligon]

Problem

ll.Feature('individual_education')() (unscoped — all declaring countries) raises instead of returning a partial assembly:

make: *** No rule to make target '.../Nepal/var/individual_education.parquet'.  Stop.
Data file .../Nepal/var/individual_education.parquet still missing after running fallbacks.

Nepal declares individual_education in _/data_scheme.yml but ships no source microdata (see the Countries Without Microdata table in CLAUDE.md: Nepal, Armenia, Timor-Leste 2001, Guatemala). The cross-country Feature assembler tries to build every declaring country and dies on the first with no data, taking the whole assembly down.

Impact

Any Feature(name)() call where ≥1 declaring country lacks buildable data fails wholesale — not specific to education. Consumers must manually enumerate the country subset that has data, defeating the no-argument convenience call.

Suggested fix

In the Feature assembly path (and/or diagnostics.load_feature), catch the missing-data / "still missing after fallbacks" error per country, emit a warning, and continue assembling the rest. Optionally record skipped countries in the result .attrs or a log line.

Evidence

Found while validating the #171 education harmonization via Feature('individual_education'). Scoping the call to the 14 countries that have data works perfectly (1.26M rows, fully canonical).

[ligon]

Closing — this was a misdiagnosis on my part, not a real defect.

Feature.__call__ already wraps each country's build in a broad try/except Exception (feature.py:261) plus an empty-frame guard (:247): a per-country failure is caught, surfaced as a warnings.warn(...), and the assembly continues. Verified directly:

ll.Feature('individual_education')(['Nepal','Uganda'])
# -> returns just Uganda (46,526 rows); Nepal is skipped with a warning. No crash.

The apparent "crash" was an interrupted slow cold build of all 29 declaring countries, whose make stderr (No rule to make target … Nepal/…parquet) and a logger.warning ("still missing after running fallbacks") I read as fatal. Country('Nepal').individual_education() does raise a RuntimeError, but that's exactly what Feature is built to absorb.

Optional polish (not blocking, recorded here): the per-country warning is the generic Failed to load … RuntimeError: …, which doesn't distinguish a structurally data-less country (Nepal, Armenia, Timor-Leste 2001, Guatemala — expected) from a genuine build error (unexpected). A nicer version would catch the specific "could not materialize / no wave-level build succeeded" condition and emit a quieter "skipped {country}: no microdata available", so real failures stand out. Minor; reopen/refile if wanted.