Write **caveman-full** by default. See [`CONTRIBUTING.md`](../CONTRIBUTING.md#caveman-style-default).

## What

<!-- What changed. Bullets OK. -->

## Why

<!-- Problem this fixes or design gap closed. -->

## Test

- [ ] `pytest tests/ -q` (if code touched)
- [ ] `python bin/check_docs.py` (if docs touched)
- [ ] ADR added if boundary/contract changed

## Links

<!-- Closes / Relates to #issue. Optional demo URL. -->