FiboaBaseConverter: make id mean something

[ivorbosloper]

Based on #264, not on main, because both touch the same file — review that one first. Four rules, each broken somewhere in the published catalog without anything noticing.

rule	what it caught
a converter must map something to id	de_bb and de_nds were published with no identifier at all — the base drops columns no mapping names, and the file validates. sk is the subtler half: index_as_id fills the column and the same drop removes it, because columns never named it
the column must be in the source	si 2019 names the field POLJINA_ID where later campaigns name it ID; 820,151 fields were written with no id, and that validated too
the values must be unique	an audit found 36 collections whose latest edition repeats an id: es_cl gave 9,109,136 fields the id "0", us_usda_cropland 3,093 ids to 7.5M fields
not both sources and variants	sources wins, so --variant 2011 converts whatever sources points at — hr would have published thirteen copies of one file

The uniqueness check runs before geometries are exploded and ignores rows with no id (those are #264's bounded drop), and it reads tuple targets, because de_sh maps FLIK to both flik and id.

CI stays red until #246, #244 and #241 land — the sweeps run over every converter, and those three still fail on main. That ordering is the point.

🤖 Generated with Claude Code

https://claude.ai/code/session_01DVx9uQV2QPM8ecPAY3ZjXG

[ivorbosloper]

vecorel-cli 0.2.18 carries this upstream. Its BaseConverter now drops rows that cannot validate under max_dropped_share, reads the required properties from the declared schemas (which is what @m-mohr asked for on #264 — no list in a converter), checks id uniqueness, refuses a converter that declares both sources and variants, and fetches the schemas before any source data.

#280 bumps the pin and brings along the two converter fixes the checks fire on (hr's rolling sources, Europe-LAND's empty crop_code). What is left of this PR that is not upstream is the sweep tests over every converter in this repository; I will carry those into #280 rather than keep this branch alive. Closing.

[m-mohr]

We should still discuss whether we apply a semantic to the id field. Some have stable IDs now, some are just row indeices.