Fix a wrong declension (the right way)

The library is gated at 100% coverage / 0 failing slots against Voikko + the corpus. Every change keeps it there. The workflow for fixing or adding a form:

1. Reproduce

keinontolibrary decline <word> --number <n> --case <c>

Decide whether it’s a rule problem (a whole class is wrong), a lexical one (one irregular word), or a gap (no form at all).

2. Mint Voikko-verified gold data

Never hand-write forms from memory — mint them. The finnish-testgen skill pulls the fi.wiktionary table and validates every form through Voikko:

DYLD_LIBRARY_PATH=/opt/homebrew/lib .venv/bin/python \
  .claude/skills/finnish-testgen/scripts/mint_testdata.py <word> \
  --kotus data/sources/nykysuomensanalista2024.txt

3. Make the fix at the right altitude

Rule — edit the class arm in crates/keinontolibrary-rules/src/generate.rs (or the gradation/harmony helpers). Prefer generalizing over special-casing.
Irregular — add Voikko-verified rows to crates/keinontolibrary-rules/exceptions.toml (the registry rejects duplicate keys and is CI-capped).
Override — for harmony / comitative / citation quirks, regenerate the sidecar (scripts/qa/run.sh harmony) rather than editing forms by hand.

Add a unit test with the Voikko-verified forms next to the change.

4. Run the gate

scripts/qa/run.sh quick      # while iterating (sampled)
scripts/qa/run.sh all        # full: ingest -> dump -> verify -> report --gate

The gate fails on any new failing slot or coverage drop. If a slot genuinely cannot be judged by Voikko (a lemma outside its lexicon, a Kotus↔Voikko disagreement), add it to qa/accepted.jsonl with a reason — never re-baseline over a real regression. Update the baseline only in the same PR as the fix:

scripts/qa/run.sh report -- --update-baseline

5. Standard checks

cargo fmt --all && cargo clippy --all-targets --all-features -- -D warnings && cargo test --all-features

CI additionally runs the MSRV build (1.85) and cargo-audit. See scripts/qa/README.md for the loop’s internals.